1878.] *-*-• [Houston and Thomson, 



Indeed it would seem that future improvements in obtaining light from 

 electrical currents will rather be by the use of a sufficient resistance in the 

 most limited space practicable, thereby obtaining in such space the highest 

 possible temperature. 



Perhaps the highest estimate that can be given of the efficiency of Dyna- 

 mo-Electric-Machines as ordinarily used, fs not over 50 per cent. Our 

 measurements have not given more than 38 per cent. Future improvements 

 may increase this proportion. Since the efficienc3 r of an ordinary steam en- 

 gine and boiler in utilizing the heat of the fuel is probably overestimated 

 at 20 per cent., the apparent maximum percentage of heat that could be re- 

 covered from Ihe current developed in a Dynamo-Electric-Machine, would 

 be overestimated at 10 per cent. The economical heating of buildings by 

 means of electricity may therefore be regarded as totally impracticable. 



Attention has, long ago, been directed to the use of Dynamo-Electric 

 Machines for the conveyance of power. Their employment for this pur- 

 pose would indeed seem to be quite promising. Since in this case one ma- 

 chine is employed to produce electrical currents, to be reconverted into 

 mechanical force by another machine, the question of economy rests in the 

 perfection of the machines and in their relative resistances. 



In respect to the relations that should exist between the external and in- 

 ternal work of Dynamo-Electric Machines, it will be found that the great- 

 est efficiency will, of course, exist where the external work is much 

 greater than the internal work, and this will be proportionately greater as 

 the external resistance is greater. Our measurements gave in one instance 

 the relaton of .82 ohm. of the arc to .49 ohm of the machine, a condition 

 which indicates economy in working. The other extreme was found in 

 an instance where the resistance of the arc was 1.98 ohms., while that of 

 the machine was 4.60 ohms, a condition indicating wastefulness of power. 



Stated Meeting, Nov. 15, 1878. 



Present, 23 members. 



Vice-President, Mr. E. K. Price, in the Chair. 



Letters of acknowledgment were received from Prof. 

 Steenstrup, of Copenhagen, dated Oct. 15, 1878 (101); the 

 R. Zoological Society, Amsterdam, Oct. 15, 1878 (101 ; Cata- 

 logue, part iii); Teyler Foundation, Leyden, Oct. 26 (101); 

 Astronomical Society, Leipzig, Oct. 26 (101); Astronomical 

 Observatory of the Eoman College, Oct. 29 (96); Royal 

 Academy of Sciences, Lisbon, April 23 (99); Royal Obser- 

 vatory, Greenwich, Oct. 29 (101); Prof. B. Pierce (101); 

 Buffalo Society of Natural Science, Nov. 12 (101); and the 

 Public School Library, St. Louis, Oct. 28 (Catalogue i, ii, iii). 



