30 RE POET OF THE SECRETARY. 



the cost of them has been more than repaid by the services they have 

 rendered to science in the Arctic expedition under Dr. Kane, and in 

 the results which have already been obtained from them in Mexico. 



The self-registering apparatus in the observatory on the Smithso- 

 nian grounds, established at the joint expense of the Coast Survey 

 and the Institution, has continued to record the variations in the 

 horizontal direction of the magnetic force during a considerable por- 

 tion of the past year. The interruptions which have taken place have 

 been principally caused by the impurities of the city gas, the exhala- 

 lations from which have interfered with the photographic process. 

 The records obtained, however, will furnish valuable data for study- 

 ing, in connexion with similar observations in other parts of the 

 globe, the character of the magnetic force, and to assist in determin- 

 ing how far the changes are merely local, or to what extent they 

 affect the whole earth. 



Laboratory. — During the past year the laboratory has been under 

 the charge of Dr. E. W. Hilgard, recently appointed State geologist 

 of Mississippi. Among others, a series of experiments was made by 

 him, under direction of the Secretary, at the expense of the Navy 

 Department, relative to the vapor from a modification of bi-sulphuret 

 of carbon as a substitute for steam applied to mechanical purposes. 

 The result of these investigations was unfavorable to the substitution 

 of this material in the way proposed. Although a greater amount of 

 pressure is produced at the same temperature than in the case of 

 steam, yet the amount of work relative to the absolute quantity of 

 heat employed is by no means in accordance with this, the density of 

 the vapor and its greater specific heat require a corresponding amount 

 of fuel^ and when we consider the fact that the bi-sulphuret of carbon 

 is not a natural but a factitious substance, of which the vapor, when 

 combined with air, is highly explosive and extremely ofiensive on 

 account of its odor and the greater complexity of the engine required 

 for its use, its application in the place of steam would be far from 

 advantageous. 



Another series of investigations was conducted in the laboratory 

 relating to the prevention of counterfeiting bank notes, particularly 

 by photography ; but as this was intended especially for private use, 

 the expenses were paid by the parties interested. 



The Institution does not consider it a part of its duty to volunteer 

 an opinion as to the practicability of the new projects with which the 

 public mind is frequently agitated ; but when directly called upon by 

 the government or other parties of influence to pronounce a judgment 



