Summarize the following court judgment. ivil Appeals Nos. 322 & 323 of 1976. From the Judgment and Order dated 27.3.1973 and 23.5.75 of the Delhi High Court in F.A.O. (O.S.) No. 35 of 1969 and C.M. No. 1300 of 1974 in F.A.O. (O.S.) 35 of 1969. P.P. Juneja for the Appellant. B.B. Barua	 Ms. A. Subhashini (N.P.) and Ms. Indira Sawhney ( N.P. ) for the Respondent. The Judgment of the Court was delivered by S.C. AGRAWAL	 J. Civil Appeal No. 322 of 1976 This appeal by special leave has been filed against the judgment dated March 27	 1973 of the High Court of Delhi in F.A.O. (O.S.) No. 35 of 1968. The appellant	 section Harcharan Singh	 was awarded a contract for 80 constructing approaches to the Bridge Structure B 2 on the North Sikkim Road in 1959 60. Under the agreement the appel lant was required to do hard rock cutting to the extent of 7.54	530 cft. The rate fixed for the said work in the con tract was Rs.129 per thousand cft. plus 2%. The appellant was required to perform hard rock cutting to the extent of 18	 18	704 cft. The appellant claimed payment at the rate of Rs.200 per thousand cft. for the additional work of hard rock cutting. He also claimed certain other sums under other heads. The dispute in respect of four heads was referred to arbitration in accordance with the clause 25 of the agree ment. The arbitrator gave his award dated February 5	 1965 wherein he disallowed the claim of the appellant in respect of two items but made an award in favour of the appellant in respect of two items of claim. In this appeal we are only concerned with the claim of the appellant in respect of the additional work of hard rock cutting which the appellant was required to execute. The arbitrator awarded a sum of Rs.52	800 against the said item. The award was filed in the High Court by the arbitrator alongwith his letter dated June 6	 1968. Objections were filed by the respondent under Sections 30 and 33 of the (hereinafter referred to as 'the Act '). The said objections were consid ered by the learned single Judge of the Delhi High Court and by order dated April 23	 1969. the said objections of the respondent were rejected and it was ordered that the award be made a rule of the Court. The respondent filed an appeal against the said order and decree passed by the learned single Judge. The appeal was partly allowed by the Division Bench of the High Court by judgment dated March 27	 1973	 whereby the award as regards the claim for higher remunera tion at the rate of Rs.200 per thousand cft. for the addi tional work of hard rock cutting was set aside. The award in respect of other item of the claim relating to expenditure incurred by the appellant in reconstructing the retaining walls after damage	 was maintained. Aggrieved by the said decision of the Division Bench of the High Court the appel lant has filed this appeal after obtaining special leave. As indicated earlier	 this appeal is confined to the claim of the appellant for payment for the additional work of hard rock cutting which the appellant was required to execute. The appellant has claimed a higher rate of Rs.200 per thousand cft. for this additional work. Under the agree ment the appellant was required to execute hard rock cutting to the extent of 7	54	530 cft. but actually he was required to execute such cutting to the extent of 18.15 lacs cft. The extent of the additional work was about 10.60 lacs cft. 	 i.e. about 140%. While undertaking the execution of the additional work of hard rock 81 cutting the appellant in his letter dates August 24	 1960 addressed to the Executive Engineer	 Central Division No. II	 Gangtok	 had requested for revision of the rate for hard rock cutting and stated that the minimum working rates for this item are 52% above the tendered rates. The ExecUtive Engineer by his letter dated September 2	 1960	 requested the appellant to submit an analysis of rate for hard rock cutting. The appellant submitted his analysis of rates on September 14	 1960 wherein after analysing the rates of materials and labour the workable rate worked out to Rs.200 per thousand cft. The Executive Engineer also got an analy sis of rates done on the basis of the data collected on actual observation and he arrived at a figure of Rs.237 per thousand cft. By his letter dated November 9	 1961 addressed to the Superintending Engineer	 Calcutta Central Circle No. III	 CPWD	 Calcutta	 the Executive Engineer recommended the extra rate of Rs.200 per thousand cft. for work in excess of 20% of the stipulated quantity. The Superintending Engineer	 in his letter dated February 23	 1962 addressed to the Additional Chief Engineer III	 Central P.W.D.	 New Delhi	 made a similar recommendation and the Additional Chief Engineer made a similar recommendation in his letter dated July 16	 1962 addressed to the Secretary to the Government of India	 Ministry of Works and Housing. It appears that the Government did not agree to pay at a rate in excess of the rate of Rs.129 per thousand cft. plus 2% stipulated under the agreement. The dispute was	 therefore	 referred to arbitration. The arbitrator in his award has considered this item of claim as under: Claim Dispute Award "The contractor claims The arbitrator The claim of the that for Item No 3 of is to deter contractor is the agreement he should mine whether partly justified. be paid at the rate of under the He should be paid Rs.200 per 1000 cft. terms and con an amount of for the quantities ditions of the Rs.52	800 (Rupees beyond what is stipu contract	 the fifty two thousand lated in the agreement. claim is jus and Eight hundred tified and if only) in addition so	 to what ex to the payment to tent. be made to him at relevant agreement rate for the total quantity of work executed by him under this item. " 82 Before the learned single Judge it was submitted on behalf of the respondent that the award is a speaking award and from the award it is apparent that the arbitrator has fixed rates for additional work done by the contractor which the arbitrator has no jurisdiction to do by reason of clause 12 of the agreement between the parties which provides that additions to the contract work shall be carried out by the contractor on the same conditions in all respects on which he agreed to do the main work and at the same rates as specified in the tender for the mainwork. The learned single Judge rejected the said contention and held that the arbi trator was determining only the value of the additional work at the rate of Rs.200 which had been agreed by the Engineer in charge and the Superintending Engineer of the Circle as contemplated by clause 12 and the scope of the inquiry before the arbitrator was only the quantity of work which was additional to the quantities specified in the agreement. The learned Judges of the Division Bench of the High Court have disagreed with the said view and have ob served that it is clear from the statement of claim as incorporated in the award	 and the affidavit of the contrac tor that there was no dispute with regard to the quantity of work and the only dispute was with regard to the rate and that the arbitrator had allowed a sum of Rs.52	800 to the contractor in respect of the total quantity of work executed by him under item No. 3 in addition to the agreed rate and that there was no escape from the conclusion that the arbi trator had awarded the above 'amount by applying a rate higher than the agreed rate. The learned Judges of the Division Bench were of the view that under clause 12 of the agreement the provision with regard to the fixing of the rate by the Engineer incharge and the Superintending Engi neer of the Circle comes into play only when the additional item of work does not form part of the main work and the rates for such work are not specified in the schedule of rates. The learned Judges of the Division Bench have held that since the additional hard rock cutting job done by the appellant was part of the main work and the agreement pro vided the rate for the said item	 there was no occasion for the Engineer in charge or the Suprer intending Engineer to fix the rate for the extra quantity of hard rock cutting and that the action of the arbitrator in allowing the rate to the contractor in excess of the agreed rate for the job of hard rock cutting was against clause 12 of the agreement and thereby the arbitrator had exceeded his jurisdiction. As regards the award of an arbitrator under the Act. the law is well settled that the arbitrator 's adjudication is generally considered binding between the parties for he is a tribunal selected by the parties and the power of the court to set aside the award is restricted to cases 83 set out in section 30 of the Act	 viz. (a) if the arbitrator has misconducted himself or the proceedings; or (b) when the award has been made after the issue of an order by the Court superseding the arbitration or after arbitration proceedings have become invalid under Section 35; or (c) when the award has been improperly procured or is otherwise invalid. Under clause (c) of Section 30 the Court can set aside an award which suffers from an error on the face of the award. It is. however. not open to the Court to speculate	 where no rea sons are given by the arbitrator. as to what impelled the arbitrator to arrive at his conclusion. But the jurisdiction of the arbitrator is limited by the reference and if the arbitrator has assumed jurisdiction not possessed by him	 the award to the extent to which it is beyond the arbitra tor 's jurisdiction would be invalid and liable to be set aside (See: Jivarajbhai Ujarnshi Sheth and Others vs Chin tatnanrao Balaji and Others	 ; This posi tion at law has been reiterated by the Constitution Bench of this Court in its recent decision in Raipur Development Authority and Others vs M/s Chokharnal Contractors and Others	 [1989] 2 S.C.C. 721. It has been held that an arbi trator or umpire is under no obligation to give reasons in support of the decision reached by him unless under the arbitration agreement or the deed of submission he is re quired to give such reasons and if the arbitrator or umpire chooses to give reasons in support of his decision it is open to the Court to set aside the award if it finds that an error of law has been committed by the arbitrator or umpire on the face of the record on going through such reasons and that an award can neither be remitted nor set aside merely on the ground that it does not contain reasons in support of the conclusion or decisions reached in it except where the arbitration agreement or the deed of submission requires him to give reasons. In the instant case the arbitration agreement or the deed of submissions did not require the arbitrator to give reasons and	 therefore	 the award cannot be questioned on the ground of an error on the face of the award. The learned Judges of the Division Bench of the High Court have set aside the award in relation to claim No. 1 relating payment for additional work of hard rock cutting on the ground that in making the award the arbitrator exceeded his jurisdiction by allowing a rate to the contractor in excess of the agreed rate for the job of hard rock cutting against the terms and conditions contained in clause 12 of the agreement. The question which needs to be considered here is as to whether in awarding the sum of Rs.52	800 to the appellant for the additional 84 work of hard rock cutting executed by him the arbitrator has disregarded clause 12 of the agreement. The said clause reads as under: "The Engineer in charge shall have power to make any altera tions in	 commissions from	 additions to or substituting for	 the original specifications	 drawings	 designs and instructions	 that may appear to him to be necessary or advisable during the progress of the work	 and the contrac tor shall be bound to carry out the work in accordance with any instructions which may be given to him in writing signed by the Engineer in charge	 and such alterations	 omissions	 additions or substitutions shall not invalidate the con tract: and any altered	 additional or substituted work which the contractor may be directed to do in the manner above specified as part of the work shall be carried out by the contractor on the same conditions in all respects on which he agreed to do the main work and at the same rates as are specified in the tender for the main work. The time for the completion of the work shall be extended in the proportion that the additional or substituted work bears to the Origi nal work	 and the certificate of the Engineer in charge shall be conclusive as to such proportion. And if the al tered	 additional or substituted work included any class of work for which no rate is specified in this contract	 then such class of work shall be carried out at the rates entered in the schedule of rates of the C.P.W.D. Schedule of Rates 53 54 on which the estimated cost shown on page 1 of tender is based provided that when the tender for the original work is a percentage above the schedule rates the altered	 addi tional or substituted work required as aforesaid shall be chargeable at the said schedule rate plus the same percent age deduction addition and if such class of work is not entered in the said schedule of rates	 then the contractor shall within seven days of the date of the receipt of the order to carry out the work inform the Engineer incharge of the rat. e which it is his intention to charge for such class of work	 and if the Engineer in charge does not agree to this rate he shall by notice in writing be ' at liberty to cancel his order to carry out such class of work and arrange to carry it out in such manner as he may consider advisable provided always that if the contractor "shall commence work or incur any expenditure in regard thereto before the rates shall have been determined as lastly hereinbefore 85 mentioned	 then and in such case he shall only be entitled to be paid in respect of the work carried out or expenditure incurred by him prior to the date of the determination of the rate as aforesaid according to such rate or rates as shall be fixed by the Engineer in charge. In the event of a dispute the decision of the Superintending Engineer of the Circle shall be final. " Under this clause the Engineer in charge was empowered to make any additions to the original specifications that may appear to him to be necessary or advisable during the progress of the work and the contractor was bound to carry out the work in accordance with any instructions given to him in writing signed by the Engineer in charge. As regards payment for the additional work which the contractor was directed to do it was provided that: (i) The contractor shall be paid at the same rates as are specified in the tender for the main work; (ii) If the additional work included any class of work for which no rate was specified in the contract then the con tractor shall be paid at the rates entered into the schedule of rates of the C.P.W.D. Schedule of Rates 53 54 on which the estimated cost shown on page 1 of tender is based and if the tender for the original work is a percentage above the schedule rates the additional work shall be chargeable at the said schedule rates plus the same percentage deductions/addition; and (iii) If such class of work is not entered in the said Schedule of Rates then the contractor should inform the Engineer in charge within seven days of the receipt of the order the rate he wants to charge for such class of work and the Engineer in charge	 if he does not agree to the said rate	 may cancel the order for such additional work and if the contractor has commenced the work or incurred expendi ture in regard thereto before the determination of the rates the contractor shall be paid in respect of work carried out or expenditure incurred by him prior to the determination of the rates according to such rates or rates as shall be fixed by the Engineer in charge and in the event of a dispute the decision of the Superintending Engineer of the Circle would be final. The case of the appellant is that clause 12 envisages alter ations or 86 additions within reasonable limits and an addition to the extent of 140% in respect of one particular item alone is not covered by this clause and that in awarding Rs.52	800 as extra payment for the additional work the arbitrator has not acted in disregard of clause 12 and he cannot be said to have exceeded his jurisdiction. A clause making provision for additions and variations is generally found in building and construction contracts. In Hudson 's Building and Engineering Contracts 8th Edn. it has been observed: "It may be that it can be inferred from the terms of the contract that the power to order extras	 although apparently unlimited	 is in fact limited to ordering extras up to a certain value and	 in such a case	 extras ordered in excess of that amount	 although work of a kind contemplated by the contract	 may yet be quite outside the terms of the con tract." (p. 294) "If the extra work ordered is outside the contract the terms of the contract have no application." (p. 296) In this context it would be relevant to take note of the decision of the Court of Appeal in England in Parkinson (Sir Lindsay) & Co. Ltd. vs Commissioners of His Majesty 's Works and Public Buildings	 In that case the contractors had agreed with His Majesty 's Commissioners of Works and Public Buildings to erect an ordnance factory according to the general conditions and specifications and bills of quantities and drawings annexed for the contract sum of Pound 3	500	000 and under the general conditions of contract the Commissioners had power	 at their absolute discretion	 to modify the extent and character of the work or to order alterations of or additions to the works and it was the duty of the contractor to comply with the archi tect 's instructions in this respect. In the contract it was also provided that it is probable that further work to the value of approximately	 Pound 500	000 would be ordered on a measured basis under the terms of the contract. The contract was amended by a deed of variation and it was provided that exceptional methods should be used to hasten the work and that a system of uneconomic working should be introduced to bring about the completion of the factory by the date fixed by the contract. The Commissioners ordered work to be exe cuted greatly in excess of the amount contemplated although not different in character from that covered by the varied contract	 so that the works could not be completed until a year beyond the time anticipated and the actual cost of the 87 contracts was L6	683	056 which amount had been paid to them alongwith L300	000 the maximum profit under the deed of variation. During the progress of the work the contractors had. complained to the Commissioners that they were being called on to execute more work than was contemplated by the varied contract and claimed that they were entitled to extra remuneration for the work in excess of that contemplated but they proceeded with the work at the request of the Commis sioners leaving the issue to be subsequently decided by arbitration. The arbitrator found that the estimated cost of the work under the varied contract was L500	000 and awarded L90	298 as proportionate or reasonable profit or remunera tion to the contractors for the additional work. The said award was upheld by the Court of Appeal on the view that a term must be implied in the varied contract that the Commis sioners should not be entitled to require work materially in excess of the sum of L5	000	000 and that such excess work having been done by the contractors	 the Commissioners were liable to pay the contractors reasonable remuneration there fore. On behalf of the Commissioners reliance was placed on Condition 33 of the original contract which gave the Commis sioners an unlimited power of ordering extras even to the extent of altering the character of the work. The contrac tors	 on the other hand	 placed reliance on the following observations of Mc Cardie	 J. in Naylor	 Benzon & Co. vs Krainische Industrie Gesellschart	 [1918] 1 K.B.331: "It is essential to remember	 however	 that words	 even though general	 must be limited to circumstances within the contemplation of the parties. " Accepting the contention urged on behalf of the contrac tors Asquith L. J. observed: "If the original contract plus the deed are read without any implied limitation on their literal meaning	 the result	 as indicated above	 is that after L300	000 profit has been earned by the contractor	 he can be compelled to labour like the Danaids without reward or limit	 or any further "extras" which the commissioners may elect to exact from him	 'till the last syllable of recorded time. ' Only the most compel ling language would induce a court to construe the combined instruments as placing one party so completely at the mercy of the other. Where the language of the contract is capable of a literal and a more restricted meaning	 all relevant circumstances can be taken into account in decid 88 ing whether the literal or a more limited meaning should be ascribed to it". (p. 662) Similarly Singleton L.J. has observed: "1 find myself unable to agree with the submission of Mr. Rewcastle that under the contract as varied by the deed of variation	 the contractors would have been bound to continue making alterations and additions	 if ordered	 for years and years	 without any extra payment by way of profit. That would have led to manifest absurdity and injustice	 as Mathew	 J. said in Bush vs Whitehaven Trustees	 (1). There must be a limit." (p. 673) Here also the question has often arisen whether the contractor under the variation clause is liable to execute the extra or additional quantities of the tendered items at the tendered rates to an unlimited extent. In some awards given by the arbitrators in the Central Public Works Depart ment of the Government of India the variation of the ten dered quantities under the variation clause in the contract has been restricted to 10% beyond which the contractor was entitled to claim as extras and these awards have been accepted and implemented by the Government. It appears that the standard form of contract of the Central Public Works Department has been amended and now it specifically permits for a limit of variation called "deviation limit" upto a maximum of 20% and upto such limit the contractor has to carry out the work at the rates stipulated in the contract and for the work in excess of that limit at the rates to be determined in accordance with clause 12 A under which the Engineer in charge can revise the rates having regard to the prevailing market rates (See: Gajaria 's Law relating to Building and Engineering Contracts in India	 3rd Edn.	 pages 410 412). In the instant case	 it appears that the Executive Engineer	 the Superintending Engineer and the Additional Chief Engineer in their letters dated November 9	 1961	 February 23	 1962 and July 16	 1962 respectively have ex pressed the view that the additional work under the terms of the contract may be confined to 20% and the appellant may be paid at the rates prescribed in the contract for 20% of the additional work and for the extra quantity of additional work he may be paid remuneration at the increased rate taking into account the increased costs in execution of the said work on account of the peculiar nature of the work. While considering the claim of the appellant the 89 arbitrator was required to consider the terms of the con tract and to construe the same. It was	 therefore	 permissi ble for the arbitrator to consider whether clause 12 of the contract enables the Engineer incharge to require the appel lant to execute additional work without any limit or a reasonable limit should be placed on the quantity of the additional work	 which the appellant may be required to execute at the rate stipulated for the main work under the contract. For that purpose the arbitrator could take into consideration the practice prevalent in the Central Public Works Department in this regard as well as the correspond ence between the appellant and the authorities including the letters dated November 9	 1961	 February 23	 1962 and July 16	 1962 of the Executive Engineer	 the Superintending Engineer and the Additional Chief Engineer recommending payment of remuneration at the increased rate for the addi tional work in excess of 20% of the quantity stipulated in the contract. The appellant was claiming increased rate of Rs.200 per 1000 cft. for the entire quantity of additional work. The arbitrator did not accept the said claim of the appellant in full and has partly allowed the said claim by awarding Rs.52	800 which means that the arbitrator has awarded the increased rate only for a part of the additional work of hard rock cutting which the appellant was required to execute. The arbitrator was entitled to do so on the construction placed by him on clause 12 of the contract and	 therefore	 it cannot be said that in awarding the sum of Rs.52	800 for the additional work the arbitrator has exceed ed his jurisdiction and the award is vitiated by an error of jurisdiction. In the circumstances	 we are unable to agree with the judgment of the learned Judges of the Division Bench of the High Court on this part of the claim. The appeal is	 therefore	 allowed and the judgment of the Division Bench of the High Court setting aside the award of the arbitrator with regard to item No. 1 of the claim relating to payment for additional work of hard rock cutting is set aside and the order passed by the learned Single Judge upholding the award of the arbitrator in this regard is restored. The appellant will be entitled to his costs. Civil Appeal No. 323 of 1976 This appeal is directed against the order dated May 23	 1975 of the High Court of Delhi whereby the High Court rejected C.M. No. 1300 of 1974 filed by the appellant under Order 41	 rule 21 read with Section 151 C.P.C.	 praying that the ex parte judgment dated March 27	 1973 in F.A.O. (O.S.) No. 35 of 1969 may be set aside and the appeal be re admit ted to its original number and the appeal be heard 90 and decided on merits. The appellant has filed C.A. No. 322 of 1976 against the said judgment of the High Court dated March 27	 1973 in F.A.O. (O.S.) No. 35 of 1968. The said appeal has been allowed by the judgment given today. Since the judgment of the High Court dated March 27	 1973 has been set aside by this Court in C.A. No. 322 of 1976 this appeal does not survive and it is disposed of accordingly. No costs. G.N. Appeal disposed of.

The appellant was awarded a contract for constructing approaches to certain Bridge structure. As per the agree ment	 he was required to do hard rock cutting to the extent of 7	54	530 cft. and the rate fixed was Rs.129 per thousand cft. plus 2%. Actually the appellant was required to perform hard rock cutting to the extent of 18	18	704 cft. For the additional work	 the appellant claimed payment at the rate of Rs.200 per thousand cft. He also claimed certain other sums under other heads. Dispute in respect of 4 heads was referred to arbitration. The arbitrator in his award disal lowed two claims and allowed the other two claims	 one of which was in respect of the additional work of hard rock cutting	 and awarded a sum of Rs.52	800 under this head. The arbitrator filed the award in the High Court. After consid ering the objections filed by the respondent a Single Judge of the High Court ordered that the award be made a rule of the Court. The respondent filed an appeal against the said order and the Division Bench set aside	 ex parte	 the claim for higher remuneration at the rate of Rs.200 per thousand cft. Aggrieved	 the appellant has preferred an appeal	 by ' special leave. The other appeal	 also by special leave	 is against the High Court 's rejection of the prayer for setting aside the ex parte judgment. Allowing the former appeal and disposing of the latter one	 HELD: 1. As regards the award of an arbitrator under the Act	 the law is well settled that the arbitrator 's adjudica tion is generally considered binding between the parties for he is a tribunal selected by the parties and the power of the court to set aside the award is restricted to cases set out In section 30 of the Act. It is	 however	 not open to the 77 Court to speculate	 where no reasons are given by the arbi trator	 as to what impelled the arbitrator to arrive at his conclusion. But the jurisdiction of the arbitrator is limit ed by the reference and if the arbitrator has assumed juris diction not possessed by him	 the award to the extent to which it is beyond the arbitrator 's jurisdiction would be invalid and liable to be set aside. An arbitrator or umpire is under no obligation to give reasons in support of the decision reached by him unless under the arbitration agree ment or the deed of submission he is required to give such reasons. If the arbitrator or umpire chooses to give reasons in support of his decision it is open to the Court to set aside the award if it finds that an error of law has been committed by him on the face of the record. An award can neither be permitted nor set aside merely on the ground that it does not contain reasons in support of the conclusion or decisions reached in it except where the arbitration agree ment or the deed of submission requires him to give reasons. [82H; 83A E] Jivarajbhai Ujamshi Sheth and Others vs Chintamanrao Balaji and Others	 ; ; Raipur Development Authority and Others vs M/s Chokhamal Contractor and Others	 [1989] 2 SCC 721	 relied on. 2.1 In the instant case the arbitration agreement or the deed of submission did not require the arbitrator to give reasons and	 therefore	 the award cannot be questioned on the ground of an error on the face of the award. The Divi sion Bench of the High Court set aside the award in respect of the claim relating to payment for additional work of hard rock cutting on the ground that in making the award the arbitrator exceeded his jurisdiction by allowing a rate to the contractor in excess of the agreed rate for the job of hard rock cutting against the terms and conditions in clause 12 of the agreement. [83F G] 2.2 Under clause 12 of the agreement	 the Engineer in charge was empowered to make any additions to the original specifications that may appear to him to be necessary or advisable during the progress of the work and the contractor was bound to carry out the work in accordance with any instructions given to him in writing signed by the Engineer in charge. [85B C] 2.3 It has to be inferred from the terms of the contract whether this power to order extras	 although apparently unlimited	 is in fact limited to ordering extras upto a certain value and in such a case	 extras ordered in excess of that amount may be outside the terms of the contract. 78 Parkinson (Sir Lindsay) & Co. Ltd. vs Commissioners of His Majesty 's Works and Public Buildings	 	 referred to. Hudson 's Building and Engineering Contracts	 8th Edn. 294	 296	 referred to. In some awards given by the arbitrators in the Cen tral Public Works Department of the Government of India the variation of the tendered quantities under the variation clause in the contract has been restricted to 10% beyond which the contractor was entitled to claim as extras and awards have been accepted and implemented by the Government. It appears that the standard form of contract of the Central Public Works Department has been amended and now it specifi cally permits for a limit of variation called "deviation limit" upto a maximum of 20% and upto such limit the con tractor has to carry out the work stipulated in the contract and for the work in excess of that limit at the rates to be determined in accordance with clause 12 A under which the Engineer in Charge can revise the rates having regard to the prevailing market rates. [88D F] Gajaria 's Law relating to Building and Engineering Contracts in India	 3rd Edn.	 pages 410 412	 referred to. In the instant case	 the Executive Engineer	 the Superintending Engineer and the Additional Chief Engineer have expressed the view that the additional work under the terms of the contract may be confined to 20% and the appel lant may be paid at the rates prescribed in the contract for 20% of the additional work and for the extra quantity of additional work he may be paid remuneration at the increased rate taking into account the increased costs in execution of the said work on account of the peculiar nature of the work while considering the claim of the appellant the arbitrator was required to consider the terms of the contract and to construe the same. It was	 therefore	 permissible for the arbitrator to consider whether clause 12 of the contract enables the Engineer in charge to require the appellant to execute additional work without any limit	 or a reasonable limit should be placed on the quantity of the additional work	 which the appellant may be required to execute at the rate stipulated for the main work under the contract. For that purpose the arbitrator could take into consideration the practice prevalent in the Central Public Works Depart ment in this regard as well as the correspondence between the appellant and the authorities recommending payment of remuneration at the increased rate for the additional work in excess of 20% of the quantity stipulated in the contract. 79 The appellant was claiming increased rate of Rs.200 per 1000 cft. for the entire quantity of additional work. The arbi trator did not accept the said claim of the appellant in full and has partly allowed the said claim by awarding Rs.52	800 which means that the arbitrator has awarded the increased rate only for a part of the additional work of hard rock cutting which the appellant was required to exe cute. The arbitrator was entitled to do so on the construc tion placed by him on clause 12 of the contract and	 there fore	 it cannot be said that in awarding the sum of Rs.52	800 for the additional work the arbitrator has exceed ed his jurisdiction and the award is vitiated by an error of jurisdiction. [88G H; 89A E] 5. The judgment of the Division Bench of the High Court setting aside the award of the arbitrator with regard to the claim relating to payment for additional work of hard rock cutting is set aside and the order passed by the Single Judge upholding the award of the arbitrator in this regard is restored. [89F] 6. Since the judgment of the Division Bench of the High Court is set aside the appeal against the order rejecting the prayer for setting aside the ex parte judgment	 does not survive.