364 



Messrs. Roberts and Wrightson on the 



minutes the silver ball had not entirely melted ; the experi- 

 ment was stopped, however, as the silver began to solidify on 

 the iron stem of the ball. 



The diagram No. 3 is reduced from the original ; and 

 we have appended the calculation for fluid density, assuming 

 the position of equilibrium at first immersion of the ball to 

 be at point a. 



The particulars of the experiment are as follows: — 



1 



•v- f Diameter 

 N< \ of of ball. 

 ex V v in inches. 



5£Sd H W5E S2x 



including "ft of cold first im _ 



the stem ^'"f"' mersion, 



for attach- A ™8 the in troy 



ment. s e lp ounces. 



Deduced 

 specific gra- 

 vity of fluid 



metal. 



"Remarks. 



52. 



3 



74 ' 8 ' 10-068 ' ^ 



1 Pure silver 

 9*51 ■ ball in pure! 

 [ silver. 



The liquid density of pure silver, as determined by one of 

 us"*, on Mallet's method, from a mean of two experiments, 

 giving respectively 9 - 447 and 9*476, was 9 - 46. This confirms 

 the single result obtained by the oncosimeter. 



If we now tabulate the mean results of the foregoing expe- 

 riments, as well as those previously obtained, we shall be able 

 to compare the densities according to the two methods of inves- 

 tigation: — 



Fluid density of 



By Mallet's method. 



By oncosimeter. 





10039 



10-65 

 6-974 

 6-55 

 946 



10-055 

 8-217 



10-37 

 7-025 

 6-48 

 9-51 







Tin 



Zinc 









The difficulties connected with the working of the oncosi- 

 meter are less than those which arise in Mallet's method ; and 

 the sources of error are less, the correctness of the result in 

 the latter depending on the metal in the cone being free from 

 air-holes. 



It will be seen from the above table that, in the case of 



Roberts, Proc, Roy. Soc. vol. xxiii. p. 493. 



