n 



CONTENTS. 



Two reffels being fixed at different elevations, the lower is filled with water, and the upper with 

 air. A column of water froia the height of twenty feet is introduced into the upper veffel, 

 which condenfcs the air, and forces it into the lower. The watet from this laft is dri\'fm up 

 through an elevation of fifteen feet ; at' which period, the original (late of the vcffels is rertored, 

 that is, the water is futfered to run to wafte from the upper, and a new portion of water is in- 

 troduced into the lower, &:g. &c. Curious fad of congelation hy the expanfion of" air. 

 Remarks. 



V. Account of the Pearl Fiflicry in the Gulph of Manar, In March and April, 

 1797. By Henry J. Le Beck, Efq. (Concluded from Vol. III. p. 547.)^ 



p. 21 



VI. Procefs for extrafting Sugar from the Beet, communicated in a Letter 

 from M. Achard to Citizen Van Mons. - - - p. 28 



The root is parboiled, fliced and prefled ; the liquor ftrained, evaporated by boiling to two-thirds, 

 and cryfiallized in fhallow veffels at about 100° Fahrenheit. 



VII. Letter to the Editor from Mr. William Henry, on his Difcovery of a new 

 and improved Method of preparing the Pruffiate of Pot-afh; and on the <lif- 

 puted Queftion, whether Pruffiate of Pot-afli be decompofed by Muriate of 

 Barytes? - - - - - - p. 30 



Letter from Mr. Kirwan. Experiments of Mr. Henry. The pure pruffiate of pot-afli is prepared 

 by calcining the carbonate of barytes, diffolving it in water, and adding Pruflian blue, till it 

 ceafes to be difcoloured. Pruffiate of barytes is thus obtained in cryftals ; the powder of which 

 is gradually added to a warm folution of carbonate of pot-alh. TheTefults are carbonate of 

 barytes and pruffiate of pot-afli in crydals ; the iron being feparated by acetic acid. The car- 

 bonate of barytes may be repeatedly ufed in other proceiTes of the fame kind. Muriate of barytes 

 is decompofed by pruffiate of pot-afli, but the effeft requires fonie hours before it is apparent. 



VIII. On the Genuinenefs and Purity of Drugs and Medicines. By Mr. 

 Fred. Accum. - - - - - - p. 33 



IX. A Memoir on the Ammonluret of Cobalt, "and upon a new Acid contained 

 in the grey Oxide of that Metal, known by the name of Zaffre. By Louis 

 Brugnatelli. - - - - - - p. 36 



t> 



Glafs of cobalt not foluble in ammonia. Zaflre affijrds the oxide and an acid to that fubftance. 

 Peculiar properties of the acid. 



X. The Apparatus of Woulfe -improved, fo as not to require luting. By Cit. 

 Girard. - - - - - - p. 41 



XI. A Memoir on the Difcovery of a Quadruped of the Clawed Kind in the 

 Weftern Parts of Virginia. By Thomas JeflFerfon, Efq. - p. 4^ 



Scientific News, and Accounts of Books. - - - p. 43 



Dr. Beddoes's Leflures. Fabbroni on martial Ethiops and on Alcohol. Gren's Chemiftry. 

 tarkinfon's Chemical Pocket Book. Royal Inftitution. 



MAY. 



