158 Foreign and Miscellaneous Intelligence. 



A similar investigation has been entered into by M.Coriolis, which, 

 however, is much more refined as regards those circumstances 

 that enable the lead to resist the force applied. 



The points at first under investigation by the latter philosopher 

 were temperature, time, impact, and state of the surfaces between 

 which the lead was confined. The pieces of lead were cylinders 24 

 millimetres in diameter, and 19 in height ; weighing each from 100 

 to 101 grammes. The arbitrary scale of measurement used gave 

 680 divisions for the 19 millimetres of height. The lead was 

 pressed between two plates of iron in a kind of box, allowing lateral 

 enlargement as the pressure was exerted, and the measurements of 

 thickness were taken by means rendering the estimation very 

 delicate. 



To remove any irregularity resulting from differences in the times 

 of pressure, it was in all ordinary cases limited to an exact minute. 

 To ascertain the effect of impact, two pieces, which had been pressed 

 equally, were then re-pressed, the one for two minutes, the other 

 also for two minutes, but at eight different operations. On making 

 thus the effect of impact eight times as much in one case as in the 

 other, still the whole difference was only 19 divisions, which, di- 

 vided amongst the extra 7 impacts, gives only about 3 divisions for 

 each. As to the original temperature, its effect amounts to little or 

 nothing ; for when the cylinders were purposely cooled down, the 

 mere effect of compression evolved so much heat that they could 

 scarcely be touched, and this heat soon overpowered the original 

 difference : experimentally no sensible difference was produced. In 

 reference to the influence exerted by the state of the surfaces be- 

 tween which the lead was pressed, this also proved to be insensible. 



In the experiments the results are always expressed by the num- 

 ber of divisions to which the thickness of the lead has been reduced 

 from the original standard thickness of 680 parts ; and in this ab- 

 stract we shall only give the mean results. Under the following 

 pressures the ordinary lead used in mints was reduced to the ex- 

 pressed thickness. 



Kilogrammes . 1500 1824 ]950 3175 

 Thickness . . 463 336 337 296 



When this lead was re-fused and cast, it was found to have increased 

 so much in hardness, as with 1500 kilogrammes to give 490 

 degrees. 



Lead was then reduced from the carbonate, and tried after being 

 fused and cast once, twice, thrice, &c., care being taken as much 

 as possible to prevent oxidation by the use of tallow, charcoal, &c,, 

 upon the surface. By the pressure of 1950 kilogrammes it was, 

 after the first fusion, reduced to 333 degrees ; after the second to 

 351 ; after the third, to 398, always setting off from the standard 

 thickness of 680. 



This effect was referred to a small quantity of oxide introduced 



