The Birmingham age-herald., 1911-12-25
How They Are Guided

AV" iHNy AIc NulOeQ
 The propelling force of the rocket changes its direction with the axis along. which it acts so, without means of giv- ing stability to this axis, the trajectory would be too irregular for any practical use, but the trouble is obviated by the resistance of the air and by the rotary motion imparted to the rocket by the force of the explosion, the guiding of the projectile almost entirely depending upon the stick.
 As the composition used in the manu- facture of the rocket burns in parallel layers of uniform thickness, the amount of gas generated In a certain time or the velocity of its escape, depends upon the extent of the inflamed or burning. surface, and, In order to obtain the great est amount of inflammation, 1t Is neces- sary to form long cavity in the mass Of composition This cavity is called a bore, and. in small rockets, Is obtained by driving into the case the explosive composition in a solid mass, which is afterwards bored out This bore is made consentric with the case, and is slightly conical, and the boring forms one of the many dangers to which the makers of fireworks are subjected
 Among the decorations used as filling in rockets are stars" These are small cylindrical or cubical bodies, variously compounded, being mostly made of one part sulpheret of antimony, two parts of quartz, two of gunpowder, fifteen of ni- trate six of sulphur and two of zinc fill- ings. These materials are all pulverized separately and mixed with glue, formed into the desired shapes, dipped into gun powder. and then dried. These stars burn with a vivid white light. But. If colors are desired, the ingredient neces- sary to give the required tint is added while the materials for the stars are being mixed together.
 What the Sparks" Are
 Iron and steel filings-which must be free of dust-are used to increase the vividness of the process of combustion, and make what is technically known as Chinese brilliant fire" It is this which is thrown out by the rockets as they explode, and causes the bright sparkles as they unite with the oxygen of the air. It is these apparently trivial filings which underlie all the marvellous beauty of the 'Fountain of Gold" the "Denae Shower" and many other "set pieces" which have won the plaudts of thou sands.
 Oxygenaton takes place at the contact of the air with the particles liberatedd by the explosion of the rockets, but not In sufficient quantities to meet the neces- sity for speed to the projectile. So ni- trate of potash and chlorate of potash are puverzed and added to the other ingredients as they are mixed for using. Both of these substances are rich in oxygen, and do not cling to it as do many other chemicals, but give out the oxygen freely when heat is applied, and in so giv- ing add to combustion and the formation of vapor Sometimes the rocket maker requires a slow combustion instead of a rapid one, this being especially the case in all ''set pieces," and for this they re- sort to the use of substances which con- tain little or no oxygen, as sand, sulphate of copper and caomeL all of which are eminently fitted to retard ignition.
 Their Composition
 Many different substances enter into the composition of color for rockets, verde gris and salts of copper both give a beautiful pale green, while the sulphuret of copper. or sa lamoniac are the ground work of the rarely used, but very lovely, tint of palm or olive green. Red Is made from either calcium or lamp black. and an excess of ntre in the filling compos- sition makes a beautiful rose pink and stranium brings out the most vivid crim. son with its use. Amber, rosin and com mon salt make a brilliant golden yellow and barium and copper make light green or blue as one or the other pre- dominate in the composition used for filling.
 Roman candles are cylindrical cases charged with stars. alternating with com bustion powder, this being the same which tr ,ce1 n rncketS oplU fha cauIlac bava