CONTENTS. 



ill 



XI. A fliort Account of the Life of Pelletier. Read at the public Sitting of 

 the National Inftitute of France, the 15th Venderaiare, in the year VI. by- 

 Citizen Laffus, Secretary to the Clafs of Natural Philofophy and Mathe- 

 matics — — — — — P- 37 



XII. Extrafts from the Syfteme du Monde of M. La Place — p. 39 



Irregular figure of the terreftrial meridian. Effefts of planetary rotation. How the rotation may- 

 have been caufed by the original projeftile impulfe. On pendulums. Laws of therotation of a 

 planet, and its atmofphere. Formation of planets from the folar atmofphere. Probability 

 and effefts of a comet flrikirig the earth. Indications that fuch an event has formerly liap- 

 pened, 



XIII. On the Preparation of the concrete Acid of Lemons. By Dize, Apo- 

 thecary-in-chief to the French Army, charged with the Infpeftion of the 

 general Magazine of Medicines — — — p. 4.3 



Scheele's procefs repeated in the large way. Theoretical remarks — affinities of the purified acid. 



XIV. Ufeful Notices refpefting various Objefts. — Governor for regulating 

 the Motions of Steam Engines — Amelioration of Oil — — ?♦ 46 



Mr. Bunce of the admiralty invented the governor for fleam engines — Different methods of purify- 

 ing oil. 



New Publications — — — — ?• 47 



Sraeaton's Reports, with an account of the Society of Civil Engineers. 



MAY 1798. 



I. On the maintaining Power of Clocks and Watches — — P- 49 



Eflential requifites in the maintaining power of a good time-piece. Caufes of irregularity and their 

 remedies. Efcapements. Defcription of the crown-wheel efcapement. Its great antiquity; 

 advantages and defers. Anchor-pallets and fwing-wheel. Graham's dead-beat, in what re- 

 fpeds beneficial. Horizontal efcapement; invented in 1704. Free efcapement, with a pallet 

 and detent for watches ; invented in 1704. Free efcapement, with a pallet and detent for watches; 

 invented in 1 748 by Le Roy. Its good qualities. Variation adapted to a clock. Mudge's de- 

 tached efcapement. Comparifon of this with the pallet and detent. Detached efcapement 

 of Gumming organized and publifhed before that of Mudge. Adaptation of Mudge's invention 

 to a clock. A new efcapement for a clock ; requiring no oil, having no detent, nor aftion during 

 the time of repofe. 



II. Copy of a Letter from ProfeflTor Wilfon, of Glafgow, on the Art of mul- 

 tiplying Copies of engraved Plates and Stamps in relief. — p. 60 



The greateft difficulty of printing from glafs plates arifes from their fragility. It may be obviated by 

 cementing them to metal. Taffi's impreffions in glafs from engraved plates. Great utility of 

 fuch copies for printing. Copies of wood cuts by the fame method. 



b a in. In- 



