58 



THE COMPRESSIBILITIES OF THE MORE IMPORTANT 



The manganese, chromium, and molybdenum were all used in the form 

 of small broken pieces, treated essentially in the way recommended for 

 powders. Some difficulty was experienced in the last case from minute 

 cracks, but it is believed that the final results are free from error from this 

 cause. These various preparations of metal were one by one subjected to 

 pressure under mercury in several glass jackets in the manner so often 

 described. The mercury was all carefully purified by recognized methods. 



THE APPARATUS. 



The various jackets used for this work have been described in the fore- 

 going papers. Of these, jacket v was that used for the determinations of 

 the alkaline metals already discussed, and jacket vi was exactly similar to 

 it, having been made out of a piece of the same glass tube; jacket vni was 

 of similar form, but was larger; jackets in and ma were of a somewhat 

 different form,* used before the other form had been devised, and on the 

 whole less convenient to manipulate, but no less accurate in operation than 

 jacket v; in had already been used for sulphur; ma was made from in 

 after this had been accidentally broken, and the weights of mercury 

 needed to fill it at various pressures were calculated from those found for 

 m, through the bracketed value in the last column of the table given below. 

 For each of the other jackets these weights were determined by special 

 series of experiments, recorded below. 



Data concerning glass jackets filled with mercury. 



The data for these jackets are repeated together in the above table for 

 convenience of reference. The table is so similar to others which have 

 been given before that no further explanation is needed, except as regards 

 one point concerning it. The last column is printed to show the differ- 

 ences caused by differences in the kind of glass used in the jacket; it gives 



*See fig. 5, p. 32. 



