S48 Description of a Hydro -pntumafAc Talle 



would still be wanting, chiefly with regard to our know- 

 ledge of ihe constitution ot mineral bodies, if Bcrgmaa 

 had not pointed out the eflccts of the blowpipe, an instru* 

 ment of the greatest value lo the niincralogical chemist. 



What a deal of trouble and expense, as well as time, 

 (that most inestimable of all \.\\z desiderata of experimental 

 research,) is saved by the form which Nicholson has given 

 to the graviraeter, an instrument which renders the modes 

 of ascertaining the specifjc gravities of solids and fluids, 

 at once easy, expeditious, and accurate, to the fifth figure 

 of the dcciuial, water being taken as. unity *. 



What a vast field of inquiry has been opened to the 

 chemical philosopher by the very simple modification of 

 the air-thermometer of Leslie, — an instrui^ent of uncom- 

 mon delicacy, employed by him with the greatest advantage 

 in his in)portant researches concerning the mensuration of 

 the force and density of light ! and with what ease, expedition 

 and ceconomy are at present performed (even in the closet} 

 those operations which in former times demanded a regular 

 laboratory 1 The moveable furnace of Dr. Black f, the blast 

 furnace of Aikin, and the lamp furnace of Guiton, are now 

 considered as sufficient for carrying on, in the small way, 

 all those operations of the science, in which either a very 

 intense or a very low heat is nccessarv. These apparatus 

 alone, it may be said, have banished from the laboratory a 

 numljrr of unwieldy and cosdy contrivances, w'iiich served 

 only to excite embarrassment and confusion. Many tedious 

 processes in the practice of our science have thus been 

 iTiade easy by the help of modern instruments, hazardous 

 ones are become safe, expensive ones cheap, and the means 

 of experimenting have been brought to every door. The 

 cultivators of chemical science who have no access to the 

 laboratory of the operative chemist, are too well acquainted 



• It does not anpear that any better instrumpnt for fin «ling specific gra- 

 vities for the use of the cheniist need lie wished for, 'i'lic j^ravimelcr of 

 Nicholsin i5 susceptible of correction for the variation of temperature, and 

 the impurity of tiie water in wljich it i^ to be irumervd, wliich for practice 

 !■» sometimes more convenient. It requires no addles* in usinp it, and the 

 price at which the insu-u:neni may be purcliased is far lielow that of the 

 most ordinary k'nd of hydrostatic balance. 



f This furnace has been considerably improved by others, since its 

 first introductipn into practice. It }» very substantial, durable, not liable to 

 ba easily injured by external blows, and capable of producing a degree of 

 beat more than sufficient to mtlt iron. It ig perfectly siJe m a room; and 

 the thjckne^s of tJie walls, composed of fire bricks, with which it is lined, 

 prevents the operr.tor from being molested by the heat wlien the furnace is 

 lu actiisn. See •* Manual of Analytical Mineraiof>;y, intended to facilitate 

 the practical Analysii Q,i Mincrab," by ¥. Accuui, ^d edit, page :iij. 



with. 



