ir CONTENTS. 



APRIL 1802. 

 Engravings of the following Objects : 1. The Rev. Mr. Pearfon's Projection of 

 the Orbits of the Earth, and the new Planet Ceres. 2. Apparatus by which 

 Mr. Murray has fhewn that Fluids conduct Heat downwards, when the VeflTel 

 is effectively a Nonconductor. 3. Mr. De Lafons's free Efcapement for 

 Time Pieces. 4. Mr. Arkwright's Engine for raifing Ores from Mines. 

 And, 5. A cheap, fimple, and accurate perfpective Inftrument, by R. L. 

 Edgeworth, Efq. 



I. Experiments on the Tranfmiffion of Heat downwards through Mercury 

 and through Oil contained in VefTels of Ice; by which thofe Fluids are 

 proved to be proper Conductors of Heat. By John Murray, Lecturer in 

 Chemiftry, Materia Medica, and Pharmacy, at Edinburgh. Communi- 

 cated by the Author. - - - - Page 241 



II. Defcription of a new Efcapement for Watches, invented by Mr. John De 

 Lafons. - - - - - -251 



III. Remarks on the Proceffes for clarifying Liquids. By Citizen Parmentier. 



253 



IV. On the Difcovery of the Arfeniates of Copper and of Iron. By a Corre- 

 fpondent. - - - - 258 



V. On the Nature and Preparation of drying Oils; with a View to the Im- 

 provement of fuch as are ufed by Artifts, as Vehicles for Painting. By 

 Mr. Timothy Sheldrake. - - - - - 25.') 



VI. On the Native and Artificial Sulphurets of Iron. By ProfefforProuft. 269 



VII. General 'Obfervations on the Caufes which influence the Weather in Eng- 

 land, and the popular Methods of judging of the Weather. By James 

 Capper, Efq. formerly Colonel and Comptroller General of the Army 

 and Fortification Accounts on the Coaft of Coromandel. - 275 



VIII. Defcription of a cheap, fimple, and portable Inftrument, for deter- 

 mining the Pofitions of Objects in taking a Picture from the Life. By 

 R. L. Edgeworth, Efq. - - - - 281 



IX. Concerning the new Planet Ceres. In a Letter from the Rev. William 

 Pearfon, including an Extract of a Letter from the Baron De Zach to 

 Mr. Edward Trough ton. - 284 



X. Entertaining chemical Experiments ; with Notices of various new Facts and 

 Obfervations refpecting the Products of Nature and Art. By Mr. Frede- 

 rick Accum. Communicated by the Author. - - 295 



XI. The Method of cryftallizing Lime. By Tromfdorff. - 302 



XII. On the Cryftallization of the Hidrofulphuret of Soda. By Cit. Vau- 

 quelin. - -_.... S03 



XIII. Memoir refpecting a new Combination difcovered in Zaffre, which Cit, 

 Brugnatelli fuppofed to be a peculiar Acid, which he denominated the Co- 

 baltic Acid. By Cit. Darracq. - - 304 



XIV. On the Plumb Line and Spirit Level. By Ezekiel Walker. Com- 

 municated by the Author. - - 309 



XV. Defcription of a Machine for raifing Ore from Mines. By Mr. T. 

 Arkw'right, of Kendal, Weftmoreland. - - 313 



XVI. Curious Properties of Prime Numbers, taken as the Divifors of Unity. 

 By a Correfpondent. - - - - 314 



Scientific News. Extract of a Letter from Mr. W. Walker, Lecturer iu the 

 Eidouranion, on the new Planet Ceres.— Extract of a Letter from M. Zach, 

 Director of the Obfervatory of Gctha, to C. Mechain, of the Inftitute, Ad- 

 miniftrator of the Obfervatory at Paris.— Spiders' Webs to form the crofs 

 Wires in the Eye Piece of Aftronomicai and other Inttruments. — Thick Iron 

 burned in Oxigen.— Extreme Accuracy of tuning Mufical Inftruments. 



317 to 320 

 ERRATA. 

 I have obferved no Errata by which the Reader can be milled, but muft remark, that 



the table at page 73, called Obfervations of the Ceres is wrong intitled : the table being 



merely an ephemeris, calculated for re-difcovering the planet from the former obfervations 



of Piazzi. 



