SPEECH OF SIR WILLIAM ARMSTRONG. 383 



I shall make but slight allusion on this occasion, is intimately con- 

 nected with the dynamical theory of heat. When gunpowder is 

 exploded in a cannon, the immediate effect of the affinities by 

 which the materials of the powder are caused to enter into new 

 combinations is to liberate a force which first appears as heat, and 

 then takes the form of mechanical power communicated in part to 

 the shot and in part to the products of explosion, which are also 

 propelled from the gun. The mechanical force of the shot is re- 

 converted into heat when the motion is arrested by striking an 

 object, and this heat is divided between the shot and the object 

 struck, in the proportion of the work done or damage inflicted 

 upon each. These considerations recently led me, in conjunction 

 with my friend Captain Noble, to determine experimentally, by the 

 heat elicited in the shot, the loss of effect due to its crushing when 

 fired against iron plates. Joule's law, and the known velocity of 

 the shot, enabled us to compute the number of dynamical units of 

 heat representing the whole mechanical power in the projectile, and 

 : by ascertaining the number of units developed in it by impact, we 

 arrived at the power which took effect upon the shot instead of 

 the plate. These experiments showed an enormous absorption of 

 power to be caused by the yielding nature of the materials of 

 which projectiles are usually formed ; but further experiments are 

 required to complete the inquiry. 

 ********* * ^ 



ASSIMILATING OP MEASUREMENTS. 



Another subject of a social character which demands our consi- 

 deration is the much-debated question of weights and measures. 

 Whatever difference of opinion there may be as to the comparative 

 merits of decimal and duodecimal division, there can, at all events, 

 he none as to the importance of assimilating the systems of measu- 

 rement in different countries. Science suffers by the want of uni- 

 formity, because valuable observations made in one country are in 

 a great measure lost to another from the labours required to con- 

 vert a series of quantities into new denominations. International 

 commerce is also impeded by the same cause, which is productive 

 of constant inconvenience and frequent mistake. It is much to 

 be regretted that two standards of measure so nearly alike as the 

 English yard and the French metre should not be made absolutely 

 identical. The metric system has already been adopted by other 

 nations besides France, and is the only one which has any chance 

 of becoming universal. We in England, therefore, have no alter- 



