60 MR J. Y. BUCHANAN ON THE 



not displaced on account of the shrinkage in bulk of the hydrometer due to lower 

 temperature = 0*003 x 2"5 = 0"0075 c.c, and its weight is "007 5 3 gram (specific gravity 

 of solution being 1 "004542). 



Hence, in correcting this value of specific gravity, the weight of solution displaced 

 by the hydrometer is 182-53030 grams + 0-00753 gram= i82'53783 grams. The weight 

 of distilled water displaced = 1 8r70496 grams. The specific gravity is therefore 

 r004583, which closely agrees with the mean specific gravity of 1-004579. 



The difference of scale reading occasioned by this difference due to temperature, and 

 which is equivalent to an added weight of 0-00753 gram, is 0-82 mm., and is quite 

 an appreciable quantity when it affects all the readings in a series to this extent. 



The importance, therefore, of the precaution for commencing the series of experi- 

 ments with the hydrometers at the standard temperature by the simple device of 

 immersing them in water at, or a little above, the standard temperature for some time, 

 and drying them before commencing the experiments, is at once apparent. 



In the following section the experimental work is embodied in a number of tables. 

 Full explanation is given for each class of tables. Supplemental work which was done 

 during the preparation of this memoir is described and discussed in later sections. 



[Tables. 



