The New York herald., 1876-09-16
HALLE7TS POINT REEF.
Progress in the Art of Excavating
Under Water.
fRIUMPHS over GREAT DIFFICULTIES
The Thames Tunnel and the Cornish Tin
llnS in England.
SUCCESSFUL ENGINEERING In AMERICA.
Chicago Tunnel and the Blossom Rock in
San Francisco Bay
H ELL SAT z WO r K S {.
History of the Undertaking and Its Progress
Toward Completion.
The Thames Tunnel and the Cornish Tin
llnrS in England.
SUCCESSFUL ENGINEERING In AMERICA.
Chicago Tunnel and the Blossom Rock in
San Francisco Bay.
H & Il G AT e WO r K S.
History of the Undertaking and Its Progress
Toward Completion.

Tho near approach Of the day fixed for the great
blast at He'll Gate East River, creates amount
Of speculation regarding that grand work, and the re-
suits likely to arise from Its successful completion.
The operations being entirely to engineering
Bcience their progress has been watched with the
greatest interest by engineers because their
will be the solution OF many a vexed problem in the
Improvement OF our rivers and harbors In order to
form proper idea of the magnitude and Importance
Of the work at Halles Point reef 1t is necessary to
briefly review the history Of subaqueous mining from
its introduction down to own time, and compare
the results obtained the art advanced from crudy
TO almost perfection.
Progress in tho art OF mining has been marked by
Its most important advances since the invention OF
gunpowder chief agent Previously very few
mining works of any importance were executed be-
Of the great difficulty experienced in excavatng
the solid formations that present themselves when
such operations carried out large scale. When
VIC come to calculate enormous labor that
essary dig the great blocks of stone which
form the objects of wonder in the massive walls OF
ancient ruins filed with admiration at the in
gcnuy, skill and perseverance Of those cnry engi-
neers, who succeeded in overcoming almost lnsu-
perabo difficulties in procuring their materials
EXCAVATIONS
There is doubt that the builders OF such .struc-
tures the Babyonian temples aud the great pyra-
mds Of Cheops used the wedge principally in separnt-
ing the big blocks from their original beds. 1t 10
probable that when the masses OF stone selected
for excavation holes drilled close together along
the lines marking their outlines. and with
their directions, nearly as possible, coincdent
with tho plane of natural cleavage. These wero
subsequently united, as it were, by system OF
oblique drilling which pierced the septi dividing tho
original holes and thus the adhesion OF tho block
Its original formation WAS reduced to q minimum
Now the wedges were introduced into the cuts so
formed aud their action ruptured the small
Meeting pieces OF rock and the block completely
detached from Its quarry bed. Such operations en-
sailed Immense labor, and tho time consumed must
have been also very great but as the works usu
ally might be said invariably performed by slaves
pnd prisoners Of the former consideration counted
for little the estimation of rulers ambitious Of erect
ing mpcrishable monuments, and the latter made
up for BY the numbers Of tho workmen. This system
evidently prevailed until the adoption OF gunpowder
ss q mining agent and improved only by the ad.
made in the art OF temroring mining tools and
in tho facilities for applying them 10 the work In hand
II is believed by writer's that the aid OF powerful
acids called In by the carly miners to assist In dis
ntcgrating the points of adhesion between the blocks
and their parent formations, but this view Is unmpor-
sant except as point detail considering the
question Of ancient mining
EARLY USE OF POWDER
was entirely confined to artillery and military mining
When the primitive gun was first used as preaching
arm at the sieces OF Constantinopo and Rhodes the
destruction of the wall dcfences invariably fol.
lowed by open assaults, and the defence limited
the erection OF obslructlons tho breach and such
other means Of delaying the advance OF the enemy
the military skill and experience OF the defenders could
suggest At later stage OF the progress OF the mill
tary mines used for the destruction we'll as
the defence of walls and bridges, and system of
cavated approaches, intreDchments and other cxpcd
enis in engineering tactics was adopted which has
been developed into the present practice Nearly all
these operations necessitated the extensive OF
powder as an explosive agent, and from tho success
which attended its application have the de pro-
lection bombshel in it's many forms, well those
terrible plans OF attack which have been fcarulIy
Illustrated during recent and particularly in the
famous assault the Confederate lines at Peters,
burg, whereby large section OF the defensive works
was lifted bodily in the air and scattered with de-
lenders py the explosion of great military mine
But 1t is Of the OF explosives the operations OF
civil engineering that present article is designed
ireat and more particularly OF their application to the
purposes OF
suBAQUEoUs RxcAvAroys. MINING, IuNyELLrNo,
and other similar undertakings for the benefit Of
merce and navigation, the chief object being to illus
trate the great difficulties dangers and advantages
tending such works and the principles OF modern
cheering which believe about TO be successful
1t the He'll Gate works on tho East River New York
sity.
brief review OF the principal works which prop
Dry cassed under the above head will be Interesting to
The reader as IL will inform him the progress OF
prepared the way for that Immediately follow
Ing II. In the Interests OF the common veal
continually striving to solve the problems presented by
nature, to speak correctly, cndeavoring
adapt natural conditions human necessities. Thus
select favorable site for city sheltered island
the or on we'll located bond OF OF
great The selection Is made because of the
general advantages of the location with reference to
prospective commercial manufacturing interests and
as the settlement increases IN importance tho inhab
ants proceed to remove local difficulties which would
OF themselves tend TO impair the future prospects OF
the city by limiting Its growth and I'M
pcding its development We deepen chan
nols, fn up swamps cut down hills enclose
mud banks, remove sunken rocks, pcrforatc noun
Iains with tunnels, and construct roadwsys over
broad rivers by bridges under them by snbsqucous
tunnels, until the original aspects OF the place dis
appear under the artificial features which the busy
hands OF man mould the face OF nature.
GREAT TRruxPns OVER MATERIAL OBSTACLES
have rewarded human enterprise within the last con-
tury which may be called tho rst Of the age OF labor
The application OF steam great motor has rcvolu-
tonizod the world and has created necessities which
never felt prior TO the days OF tho locomo-
ave and the ocean steamship. Mans ideas been
expanded in proportion the knowledge he gains OF
sbe world he lives on, and the word 'impossibc"
been replaced by that Of .inexpedent, when the
execution OF any PROJECT is deferred on ac
count Of apparent difficulty This idea filed
tho mind Of the nrst Napoleon when he discussed with
the English statesman Fox the project an inicrna
tional tunnel under The Straits OF Dover warm nd.
mircr Of his companion the Emperor glcofuly ro-
marked .Oh! c'est unc des grandcs chooses que nous
pourrons faire ensep'bie0hl II is ono or the great