84 REPORT OF THE SECRETARY. 



approached, even retuotoly, in investigations of this kind. He now has in view tbe 

 synthesis of water V)y several distinct (juantitative processes, and these involve large 

 weighings. For example, hydrogen is so light that large bulks must be taken in 

 order that the errors of weighing may not exercise an appreciable influence. In order 

 to do this, glass globes holding 20 litres are used; and their weight is considerable. 

 The ordinary analytical balances, ranging from 200 to 1.0000 grammes, arc wholly 

 unavailable for the purpose, and hence an exceptional balance, such as Riiprecht has 

 made for the International Bureau of Weights and Measures at Paris, becomes neces- 

 sary . In the ollice of our own Coast and Geodetic Survey there is a balauce approach- 

 ing these in character; so sensitive as to show the difference between two standard 

 kilogrammes placed side by side or one on top of the other. This ditfereuco in posi- 

 tion of two weights is a difference of distance from the center of the earth of a few 

 centimetres only, and yet it corresponds to a difference in weight of about .000015 

 gramme. This difference, according to Professor Mendenhall, is perfectly appreci- 

 able with the balances now in use. I can not say whether or not Riiprecht keeps 

 these finer balances in stock, but I suspect that one would have to be built to order, 

 so that some mouths would elapse before it could bo delivered. The cost should not 

 exceed $500, and the balance, after serving Professor Morley's purpose, might bo 

 returned to the Institution, where it would have permanent value. The present 

 investigation could thus be assisted with little or no actual sinking of capital, and 

 the aid to research would continue long after the single investigation of Professor 

 Morley was finished. I sincerely hope that the assistance sought may be given. 



Very respectfully, 



F. W. Clarke. 



