103 



verge on a mass of platina, it might be melted in the quantity 

 of several ounces. 



I shall conclude by stating why I prefer this instrument t© 

 that of Davy. In the first place it is less expensive ; the two 

 gas holders are not to be reckoned as parts of it, they are found 

 in every laboratory, and are, in fact, necessary to the use of the 

 other, and the blowpipe can be afforded for five shillhigs. Se- 

 condly, it does not endanger the operator, while the other is 

 fraught with peril, and even with the improvements which have 

 been made on it, it is, in no little degree, formidable ; the gases 

 are mixed in the most explosive proportion, and from their 

 compressed state, the machine may not unaptly be compared to 

 a loaded shell ; its insecurity is acknowledged by the gentleman 

 who is most dexterous in the use of it, as he finds it necessary 

 to operate behind a bomb proof. 



Thirdly, It affords greater facility in prolonging an operation. 

 With a nozzle of -V- I find that J50 cubic inches of the mixed 

 gas escape in a minute under the pressure of 6 inches ; now the 

 instruments of Newman, which I have seen, do not hold more 

 than 80 cubic inches, and without enormous condensation none 

 of them could supply such an aperture for five minutes. Now 

 we cannot enlarge its receiver without augmenting the danger 

 and the condensation is also limited, for the gases exj)lode by 

 sudden con>pression, and the syringes now used are too large to 

 be wrought slowly against a high pressure. 



Fourtlily, the effect is very little inferior, if at all ; no advantage 

 is gained by having the gases in a counnon receptacle, and very 

 little by their condensation. Could the new blowpipe be used 

 with gases, whose elasticity was no more tlian an inch or two 



