145 



Its apparent weight in air is intermediate between that of a pound 

 of platinum and a pound of brass, approaching more nearly to the 

 latter than to the former. 



Six series of weighings in water gave for the absolute weights of 

 water displaced by it at 18 C. 



2639-831 

 2639-809 

 2639-838 

 2639-825 

 2639-819 

 2639-814 



Mean 2639-823 



Whence density quartz at 18 C. = 2 . 65250()> 



density water at 18 C. 



Denoting the quartz weight by Q, and the new Imperial Standard 

 Pound by I, the comparisons of Q with I in air, reduced to a 

 vacuum, gave 



Grains. No. of Obs. 



Q= I + 2-36801 40 



Q = I + 2-36871 40 



Q = I + 2-36817 40 



Q = I + 2-36782 40 



Q= I + 2-36715 40 



Mean Q = I + 2-36797 . , 200 



Secondary Standards. 



Thirty secondary standards, of gun-metal protected by amalgam- 

 gilding, were constructed by Mr. Barrow. The densities of these 

 were determined by weighing them in air and in water, and their 

 absolute weights by comparison either with I or with T+D. 



Values of the densities at the freezing-point in terms of the maxi- 

 mum density of water, absolute weights in terms of I, and 

 apparent weights, at Somerset House in air of the temperature 



