46 REPORT OF THE SECRETARY. 



could exceed the kindness exercised by all the Dutch officials 

 of Sumatra to further the comfort and success of the observ- 

 ers. Free transportation was offered on all government rail- 

 ways, and observing sites placed at their disposal, with native 

 laborers for the installation of equipments. The Secretary 

 wishes to especially acknowledge the indebtedness of the 

 Institution to his excellency Governor Joekes, of Sumatra's 

 west coast, to Heer Th. F. A. Delprat, head of government 

 railways in Sumatra, and to Heer C. G. Veth, United States 

 consular agent at Padang, whose efforts in behalf of the party 

 were untiring. 



The little expedition reached Solok April 11 and passed the 

 time in constant drill, being strengthened by native help in 

 erecting instruments. On the momentous day (May 18) the 

 weather proved to be ver}^ bad over this portion of the island, 

 and caused the partial failure of the observations, though Mr. 

 Abbot and his companion may feel that while it was not in 

 their power to conmiand success they have deserved it. 



They returned under the same assistance from the Army 

 and Navy with which they went out, reaching Washington on 

 the 29th of July. 



Attention is called to the progress reported b}^ the Aid Act- 

 ing in Charge in perfecting devices to increase the actual 

 working sensitiveness of the galvanometer, which is an 

 indispensable companion to the bolometer the instrument 

 which perceives and measures excessively small variations of 

 temperature. 



The bolometer, it will be remembered, was invented by the 

 present writer some twenty years ago as an instrument to 

 detect radiant heat in such small quantities as could be recog- 

 nized not even by the most delicate thermometer, and which 

 were so far beyond the reach of that instrument that the 

 thermopile could not register them. It may seem to the gen- 

 eral reader that the recognition of such excessively small 

 amounts of heat can not be of practical importance, but this 

 would be like saying that the human eye was an instrument 

 of no importance to the owner, since the amount of energy 

 which enabled it to see is so inexpressibly small. 



The bolometer has been called "an eye which sees in the 

 dark," and it sees only by means of almost inlinitesimally 



