CONTENTS. 



Xi 



III. Obfervations on the Phyfical and Political Geography of North Africa. 

 By James Rennel, Efq. F.R.S. — — — , P« 253 



Dlvifion of North Africa into three parts, namely, the Northern, the Tropical, and the Defert Re- 

 gions. General view of the Defert. Phyfical and political notices concerning the tropical region or 

 Taft belt of elevated land in the parallel of 10* north. 



IV. Obfervations on Metallic Money ; chiefly directed to afcertain the raoft 

 advantageous Diftribution and Figure of Gold, Silver, and Copper, in 

 Coins — . — — — — p. 260 



Political Economy. How the commercial Intercourfe of fociety is facilitated by money. New Britifli 

 coinage in contemplation. Metallic money. The ratio of value between different metals cannot 

 be fettled by the State. Hence the national medium ought to be of one metal only, namely, gold ; 

 with the lefs valuable metals for fraftions. Adjuftment of the relative values of thefe laft. De- 

 ftruftion of coin by wear — depends on the material and the figure. Inveftigation of the bed figure, 

 Obfervations and fafts refpe&ing the figure and wear of guineas. General refults. 



V. An eafy Method of Cleaning and Bleaching Copperplate Impreflions or 

 Prints, extrafted from a Letter of Sig. Geo. Fabbroni, Sub-dire6tor and 

 Superintendant of the Royal Cabinet of Philofophy and Natural Hiftory 

 of his Royal Highnefs the Grand Duke of Tufcany, to Sig. D. Luigi Tar- 

 gioni at Naples — — — — p. 265 



InftruiSions for preparing the oxygenated marine acid by fimple mixture, and for blaiching old prints 

 ■with fafety and efFeft. 



VI. On the Propagation of the Zebra vi'ith the Afs — — p. 267 



VII. On the Procefs of Bleaching with the Oxygenated Muriatic Acid ; and 

 a Defcription of a New Apparatus for Bleaching Cloths with that Acid 

 diflblved in Water, without the Addition of Alkali. By Theophilus Lewis 

 Rupp — — _- — — p. 268 



Experiments which prove that the ufual addition of allcali to the bleaching liquor impairs its power. 

 Apparatus for performing the procefs without alkali; by which a favingof forty per cent, is gained. 



Vni. Experimental Refearches concerning the Principle of the lateral 

 Communication of Motion in Fluids, applied to the Explanation of vari- 

 ous Hydraulic Phenomena. By Citizen J. B. Venturi, Profeflbr of Expe- 

 rimental Philofophy at Modena, Member of the Italian Society of the In- 

 ftitute of Bologna, the Agrarian Society of Turin, &c. (Continued from 

 p. 179) — — — _ _ p.273 



Experiments on the qbantitj' and limits of the increaled expenditure of fluids through conical diTergent 

 *«bes. 



IX. An Account of the Means employed to obtain an Overflowing Well. 

 By Mr. Benjamin Vulliamy — — — p. 276 



A well of four feet diameter was funk and fteined to the depth of 236 feet, and then bored, and a 

 copper pipe of the diameter of 5^- inches driven through 21 feet. Water ai^d fand rofe through 



c a 96 feet» 



