CONTENTS. iik 



MARCH, 1305. 



Engravings of the following Objects: ]. An improved Air Pump with Glafs 

 Barrels^and Piftons of Metal, without leathering. By Mr. Mendlefhon ; 2. 

 Plans and Se&ions of the fame Instrument; 3. Figures to illuilrate a new- 

 Theory of the Speaking Trumpet. By Mr. Cough ; 4. Improved Apparatus 

 of Woulfe; 5. Diagram of a Method of drawing a Line in a Circle, verjr 

 nearly equal to the Side of a Square, having the fame Area. 



I. Historical and Critical Obfervations relating chiefly to the Inventiqn of the 

 Telefcope. In a Letter from E. O. - - - - 145 



IT. Conftru&ion of a Line in a Circle, nearly equal to the Side of a Square 

 of the fame Superficies as that of the Circle itl'elf. With Remarks on Pen- 

 dulums and other Objects. By Mr. J. Whitley Bofwell. - 151 



III. Some Remarks upon the Experiments by which Mr. Ez. Walker has 

 endeavoured to explain the apparent Enlargement of the Moon near the 

 Horizon; with a Statement of fome Fails upon which that Phenomenon 

 feems chiefly to depend. In a Letter from C. H. - - 15S 



JV. A Mathematical Theory of the Speaking Trumpet. By John Gough, 

 Efq. - - ' - 160 



V. Obfervations on Bafalt, and on the Tranfition from the vitreous to the 

 ftony Texture, which occurs in the gradual Refrigeration of melted Ba- 

 falt; with fome geological Remarks. In a Letter from Gregory Watt, Efq. 

 to the Right Hon. Charles Greville, V. P. R. S. From the Philofophical 

 Tranfa&ious for 1804. 165 



VI. Improved Conftrucnon of Woulfe's Apparatus. ByW.B. - 180 



VII. Obfervations on the Change of fome of the proximate Principles of 

 Vegetables into Bitumen ; with Analytical Experiments on a peculiar Sub- 

 ftance which is found with the Bovey Coal. By C. Hatchett, Efq. F. R. S. 

 From the Philofophical Tranfaftions for 1804. 181 



VIII. Account and Defcription of an improved Air Pump. By Mr. N. 

 Mendelsfhon. 201 



IX. Letter concerning Palladium, from Wm. Hyde Wollafton, Efq. M, D. 

 F. R. S. the Difcoverer of that Metallic Body. 204 



X. Short Remark on Mr. Walker's laft Letter refpe&ing Focal Images. By 

 C. L. - - - - - - - , 20S 



XI. A Communication on the Ufe of Green Vitriol, or Sulphate of Iron, as 

 a Manure; and on the Efficacy of paring and burning depending, partly, 

 on Oxide of Iron, By George Pearfon, M. D. Honorary Member of the 

 Board of Agriculture, F. R. S. From a Communication made by him to the 

 Board, and inierted in the fourth Volume of their Tranfa6fions. - 205 



XII. Letter from Mr. Accum, refpc&ing an Error itated to exift in his Prac- 

 tical Chemiftry. ._.-._ 214. 



XIII. Procefles for obtaining a durable and fuperior Lake from Madder. By 

 Sir H. C. Englefield, M. P. F.R. S. - - - 215 



XIV. The Dutch Method of curing Herrings, extracted and tranflated 

 from the German of Kriinitz's Economical Encyclopaedia (Oeconomifche 

 Encyclopedic) Article Haring, by J. Hinckley, Efq. F. S. A. 223 



APRIL, 



