viii. CONTENTS. 



SUPPLEMENT. 



Engravings of the following Objects: 1. A detached Escapement for Time* 

 pieces, by lliioiit:; being the earliest yet pointed out ; 2. Apparatus by Count 

 Runiford, for pciforming some new Experiments on the Conducting Power 

 of AVater ; communicated to this Journal by the Author ; 3. Diagram for ex- 

 plaining the Achromatic Eye-piece, by Mr. Brewster ; 4. A revolving Balance, 

 invente'd by Robert Hook; 5. Diagram by the same, for explaining the Vi- 

 brations of Pendulums ; 6. Three Drawings, exhibiting an Invention of Mr. 

 Hardy for rendering all the Vibrations of a Balance of equal Duration. 



I. Inquiries concerning the Mode of the Propagation of Heat in Liquids. By 

 Benjamin Count of Rumford, F. R.S. Read at the National Institute of 

 France, 9th June, 1806. Translated by W. Cadell. - 353 



II. An Account of the Invention of the Balance Spring, and the Determination 

 of the Conditions of its Isochronisni in wide and narrow Vibrations, by Robert 

 Hooke, in the 16th Century, and of thelirst free Escapement by Du Tertre; 

 together with various other Historical DetpJls relative to Timepieces. In a 

 Letter from Mr. Thomas Reid of Edinburgh. - - 363 



III. A Method of rendering all the Vibrations of the Balance of a Timepiece 

 equal. Ij] a Letter from Mr. William Hardy. - - 387 



IV. Remarks on Achromatic Eye-pieces. By David Brewster, A. M. 388 



V. Chemical Experiments on Guaiacum. By Mr. William Brande. From the 

 Philosophical Transactions, 1806. - . - 339 



VI. On Silver Coins. By Thomas Thomson, M. D. F. R. S. E. Communicated 

 by the Author. - . . . . 396 



VIT. On the Direction of the Radicle and Germen during the Vegetation of 

 Seeds. By Thomas Andrew Knight, Esq. F. R. S. In a Letter to the Right 

 Honourable Sir Joseph Banks, P. R. S. - - - 409 



VIII. On Thunder Storms. By Mr. Samuel Berey. - 486 



IX. Farther Commimication from E. E. respecting the Discoveries of Mayow 



419 



;?>:. Scientific News :— New Map of Scotland, '422— Medical Theatre, St. Bar- 

 tholomew's Hospital, ib. 



