tt CONTENTS. 



DEC'eMBER, 180 k 



Engravings of the following Objefls : 1. Anew Compenfation Pendulum, by 

 Mr. Edward Troughton ; 2. An Inftrument for meafuring the Abforption of 

 Gafes, by Morozzo j 3. Diagram to explain the galvanic Energy upon Water, 

 by C. Wilkinlbn, Efq. ; 4. Two Plates exhibiting a Condenfer of Forces, by 

 which the Ailion of a variable firft Mover is converted into a conftant Pref- 

 furc, by Prony, 



I. Defcription of a tubular Pendulum, having all the Properties of the Grid- 

 iron, but being more compa<Sl as well as more fteady in its Motions. In a 

 Letter fiom Mr. Edward Troughton, the Inventor - Page 225 



II. Letter from W. Jeffop, Efq. on an Improvement in the Procefs of Blarting 

 Rocks with Gun-powder - . ^ - 230 



III. On the Mucilaginous Matter of certain Vegetables, and their Ufc as a 

 Subftitute ivr Gum Arabic j by Mr. Thomas Willis; being a Continuation 

 of Experiments rpade upon the Subjeft by him, in Addition to thofe for- 

 merly pubiilhed in the Tranfaftions of the Society of Arts - 232 



IV. Examination of Mr, Ezekiel Walker's Experiments and Theory of the 

 Enlargement of the Horizontal Moon. In a Letter from C. L. 235 



V. The Method of preparing Chinefe Soy. By Michael de Grubbens 237 



VI. On the Laws of Galvanifni. In Letters from C. Wilkinfon and Thomas 

 Harrifon, Elqrs. ----- 240 



VIL Remark upon an AflTertion of Lavoifier, which has been repeated by 

 eminent Chemifts. By P. Prevoft, ProfcfTor at Geneva, and Correfpondent 

 with the National Inftitute of France - _ - 247 



VIII. Account of a Memoir on chamoying of Leather. By M. Seguin 251 



IX. Analyfis and Dccompofition of a Liquor employed to render Stuffs im- 

 permeable to Water. By M. Vauqiielin - - 252 



X. New Experiments on Abforption by Charcoal, made by Means of a new 

 Machine. By C. L. Morozzo _ _ - 255 



XI. On the Commerce of Hens Eggs, and on their Prefervation. By M. 

 Farmeniier - _ - - _ 264 



XII. Method of giving the Colour, Grain, and Hardnefs-of Steel to Copper, 

 By B. G. Sage . , _ - . 267 



XIII. Obfervations on Mr. Gough's two Letters on Mixed Gafes - 269 



XIV. Some Account <5f a Condenfer of Forces, or a Method of obtaining the 

 greateft poinble Effeft from a firft Mover, of which the Energy is fubjeft 

 to Increafe or Diminution within certain Limits j and in general to vary 

 at Pleafure the Refiftance to which the Effort of the firft Mover forms an 

 Eciuilibriiim in any Machine whatever, without changing any Part of the 

 Conftruaion. By R. Prony - - - - 275 



XV. Abftraft of a Memoir on the Poffibility of obtaining Pruffiate of Potafli 

 iree from Iron ; the Unalterability of the Fruffic Acid at high Temperatures} 

 and the true Nature of the Combinations of this Acid with different Bafes. 



. ByBuchoh - - - - - - 278 



XVI. Obi'erv;itions on the Caufe which augments the Intenfity of the Sound 

 in Speaking Trumpets. By J. H. Haffenfratz - - 283 



XVII. Account of Cerium, a new Metal found in a Mineral Subftance from 

 Baftnas, in Sweden. By W. D'Hefinger and J. B. Bergelius - 290 



Scientific News. 301 — Extract of a Letter from Mr. Bode, Aftronomer Royal 

 at Berlin, to Mr. A. F. Thoelden, ib.^-Experiment on the Heat which is 

 developed during the compreffion of the Air, 302 — Extra6l of a Letter from 

 ProfcUor P'rouft to J. C. Delametherie, ib. — Method of obtaining pure Cobalt. 

 By Tromfdorff, 303— Method of Coating Copper with Platina. By Straufs, 

 ib. 



