208 Professor Gordon an Measwe of Impact. 



Sp. gr. 2-24. I. 11. 



Peroxide of iron, . . . 59*56 64-36 



Silica, .... 14-56 13-92 



Water, 2020 



Vegetable matter, . . . 4*72 



Alumina, . . . .a trace. 



Lime, ... a trace. 



99-04 



When digested with muriatic acid, it partly gelatinizes. 



l^th February, 1844, — The President in the Chair. 



A letter was read from Mr. John Craig, stating his intention of pub- 

 lishing a work by subscription, on the geology of the Western division 

 of the Great Valley of the Scottish Lowlands. 



Mr. Keddie exhibited to the Society, in the absence of Dr. Penny, 

 specimens of sulphur from Sicily. A specimen, analysed by Mr. 

 Boyd, in his laboratory, was found to consist of 



99-8 



Dr. R. D. Thomson presented to the Society the Annual Report of 

 the Registrar General for 1842; also Quarterly and Weekly Tables of 

 Mortality for 1843 and 1844. 



The following communication was read. 



XLVII — Note on the Measure of Impact^ by pressure or weight. 

 By Professor L. Gordon. 



The object of this note was to point out that some recent attempts 

 to measure the force of impact absolutely by the registered indication 

 of a spring dynamometer, would give only comparative results, vary- 

 ing for each particular spring used. 



Supposing the spring's elasticity to be such, that equal pressure 

 produced equal elongations, it was demonstrated that its registration 

 under the influence of a weight suddenly brought upon the dynamo- 

 meter, and its acquired velocity, would bo double the elongation due to 

 the weight, supposing all acceleration of motion carefully prevented. 



