■*44 0« ^^' Supply and Application of the Blow-pipe. 



the blaft mav be regulated bv turning the cock more or lefs 

 atN. ■ ' 



When an operation is to be performed on a fuhjcfl which 

 cannot be held over the table; by fixing the Anall hofe and 

 blow-pipe ah, lig. 7, into one of the conical mouths O, o, 

 of the pipes of delivery, and, bv placing a lamp or candle on 

 the edge of the table, an operator may, with the fuVjjeCt in 

 his hand, expofe the proper fpot to the flame. In this way 

 clafs matraflfes filled with liquors have been hcrmeticaUy 

 fealed. 



Nothing can be more fteady than the llream of air emitted 

 by this inltriiment. The falling; otT in prefl'iuc, arifing from 

 the defcentof the water, does not perceptihJv affe6t the flame 

 in a blaft of fix minutes duration; and, in the mean time, 

 the hand'e may be dcprelTed fo gently, that the mott ftri6l 

 obfervalion will not dlfcover the leafl. ur.fteadinefs to be pro- 

 duced by it. O?-, if the machine be filled with air, by open- 

 ing the cock more or lefs, an equable blaft may be fupported 

 for more than the fpace of an hour. 



In order to fupplv the enamellers' lamp with air by means 

 of the hvdroltatic blow-pipe, it is only necefl!arv to fubiti- 

 tute this inftrument for the bellows con)monlv ufed for this 

 purpofe. There will then be nothing novel in the manner 

 of operating, exceptinir, ifl, That the relative fituation of the 

 flame and the pipe is to be regulated by turning the fcrew S, 

 or by Hiding backward or forward the block through which 

 it paflTes ; and, 2dlv, 'I hat in lieu of the frequent movement 

 of the foot, necelfary with the common bellows, iu the fpace 

 of one minute, and with fifteen llrokes of the handle, as 

 much air may be drawn into the hydroftatic blow-pipe as 

 will blow for one hour : and as the cafk and pipes are com- 

 pletely air-tight, the blall may be flopped, or its ftrength in- 

 creafed or diminiflied at pleafure, by turning more or lefs the 

 cock of the pipe delivering the air. 



The flame of the enamellers' lamp is not ufed exclufively 

 for the pnrpoles of the artifl from whom it takes its name. 

 It is ihi.v modification of the principle of the blow-pipe which 

 is applied to the moulding of glafs inllruments. But in heat- 

 ing glals wiih this flame, au inconvenience arlfes from the 

 impoflibility t,f expofing both fides of any fubjecl to the fame 

 heat, uiilefs it be conl'antly turned round; for, if only one 

 fide of a large glafs tube be applied to the flame, the part 

 expoftd to its a<^tion wilt be fuled before the other will be 

 lotiened, arul if it be turned round conilantly a much longer 

 time will be requir«d to nidt it. Indeed fome large tubes of 



refractory 



