C O N:iriE/K(T S. Tii 



AUGUST, 1811. 



EngraTingsof the following Subjects: 1. Diagrams illustrative Of the Motion 

 of Rockets, by W. Moore, Esq. 2. A new Thrashing Machine, invented, 

 by H. P. Lee, Esq. 3. A screw adjusting Plough, by Mr. Thomas Balls. 

 4. An improved Implement for extirpating Docks and Thistles, by Mr. 

 J. Baker. 5. A Pair of expanding Harrows, by Mr. Wm. Jeffery. 



i. On the Motion of Rockets both in Nonresisting and Resisting Medians. 

 By W, Moore, Esq. - - - - - - - - 241 



II. On the Defective Algorithm of Imaginary Quantities. In a Letter from a 

 Correspondent ----- -- - - 2i* 



IIL On the Nature of Heat By Marshall Hall, Esq. In a Letter from the 

 Author - - - - - - - - - - V - 257 



IV- On a Combination of Oximuriatic Gas and Qxigen Gas. l By Humpiiry 

 Davy, Esq. LL. D. Sec. R. S. Prof. Ciiem. R. L - - 260 



V. Description of a new Thrasliing Machine, invented by H. P. Lee, Esq. <^ 



Maidenhead Thicket . - . ^ ~ - . . 274 



VL Account of a Substitute for Hemp, prepared from Bean Stalks. By the " 

 Rev.Jamcs Hall, of Chesnut -Walk, Walthamstow - 27* 



VII. A Chemical Analysis of Sodalite, a new Mineral from Greenland. By- 

 Thomas Thomson, M. D. F. R. S. E. Fellow of the Imperial Chimr^o- 

 Medical Academy of Petersburgh - - - 235 



VIIL Account of a primitive Gypsum. By Mr. Daubuisson, Mine Engineer 292 



IX. Farther Observations on the Fructification of the Firs. In a Letter from 

 Mrs. Agnes Itoetson - - - - - - - 295 



X. Description of a Screw adjusting Plough, invented by Mr. Thomas Balls, 

 of Saxfingham, near Holt, Norfolk - - - 2j&* 



XL An improved Implement for extirpating Docks and Thistles : by Mr. J. 

 Baker, of West Cober, near Yeovil, in Somersetshire - .,^ 3t)l 



XII. Descriptionofa Pair of Expanding Harrows, applicable both for clean- 

 ing foul Land, and harrowing in Seeds. By Mr. William Jeffery, of ,Cotton 

 End, Northampton - - - - 502 



XIII. Observations on an occasional Increase and Decrease of Bulk in the Hjut 

 of the Head. In a Letter from Thomas Forster, Esq. - - 503 



XIV. On the Prevention of Damage by Lightning. In a Letter from Mr. B, 

 Cook - - - - . 505 



XV. Extract of a Letter from Mr. Cordier, Mine Engineer, on Mount- 

 Mezia ----- _ 310 



Scientiiic News - . - . . 312 



SUPPLEMENT 



