CONTENTS. ix 



water, with 'probably a little nitrous acid. The rcfidue is azote. Hypothefis refpefling the 

 aftion of Galvatiifm, and the neceffity of oxygen for its condu£l. A new and more convenient 

 Galvanic apparatus. Produdlion ot fiilminating filver. Decompofition of ammonia; and of 

 fiilphuric acid. Nitrous acid conduds the Galvanic power too well to admit of its decompofing 

 a6lion. 



V. Defcription of a Mercurial Air Pump : and of a Double-barreled Air Pirtnp. 

 By Richard Auguftus Clare, Surgeon, Jamaica. Communicated by the 

 Author - - - - _ - p. 264 



The mercurial air pump confifts of two vertical pipes containing mwcury, in one of which is a folid 

 pifton, and at the extremity of the other is a valve opening upwards. The mercury in effeft 

 anfwers the purpofe of a piflon, fitted with a degree of accuracy not to be expefled in folid 

 work. The double barreled pump has the contrivance of a hole inftead of a lower valve. Its 

 piftons have valves, but by the very happy difpofition of a cock, the effeftof the apparatus may 

 be fo changed that, inftead of both barrels working from the receiver, the one is made to clear 

 the other very powerfully from the refidnal air. Obfervations to ftiew certain imperfedlions, 

 and the ineffioacy of the lower valve in Cuthbertfon's Air Pump. 



VI. A Memoir, in which the Queftion is examined, whether Azote be a fim- 

 ple or compound Body. By Chriftopher Girtanner, Doftor of Phyfic at 

 Gottingen. (Concluded from p. 171.) - - p. 268 



VII. Account of fome Experiments made with the Galvanic Apparatus of Sig- 

 nor Volta, By Mr. Davy, Superintendant of the Pneumatic Inftitution. 

 Communicated by the Author - - - p. 275 



The leading peculiarity of Mr. Davy's method of operating, confifts in his having feparated the 

 two portions of water from each other, which include the condufling wires. Between the 

 waters the circuit was made good by the human body, or by animal or vegetable fibre ; and the 

 ef^efls, generally fpeaking, were nearly the fame as if the coniioftion of water had been entire ! 

 He has examined the gafes from water, and alfo (he operation of this method on the alkalis, the 

 ancient mineral acids, &c. 



VIII. Defcription of the Machine for kneading Dough, which is made Ufe of 

 in the Public Bake-houfes of Genoa j from a Model prefented to the Patriotic 

 Society of Milan - - - - p. 28 1 



IX. On the Ufe of Caoutchouc in Manufactures, and on the Amelioration of 

 Spirits by Age. By J. A, - - - p. 282 



X. Abftraft of a Memoir on a Method of ufing the Syphon for railing Water 

 in the Machine of C. Trouville. By Citizen Prony - p. 283 



Scientific News, Accounts of Books, &c. - - p. 286, 288 



Klaproth's Analytical Eflays. — Multiplication of Engravings in Relief.-~Rational Toy«» 



Voi-.IV.— March 1801. c OCTOBER 



