\\-ii.i.i.i.M .s //;.]//;. Y.S, 



'77 



its intrinsic advantages is, that it gives the resistance to be mea- 

 sm>,l in work clone," which is independent of the momentary 

 changes in the strength of a current, by charge or electrification, 

 that influence the temporary reading of a magnetic needle. 



It recommends itself for use on board ship, not being in the 

 slightest degree influenced either by the motion of the vessel, or 

 by the magnetic influence of its moving mass of iron. 



Its simplicity of construction is such, that each part can easily 

 \amiued and verified. 



It can be used satisfactorily by persons unaccustomed to the 

 delicate handling requisite in dealing with galvanometers, and 

 elaborate resistance scales ; it is very portable ; and lastly its 

 cheapness of construction brings it within the reach of students 

 and others, who might not be well able to afford an expensive 

 apparatus. 



The following tables of actual measurements of resistances, 

 made by Mr. Liidtge, Ph.D., shows the degree of accordance 

 between the findings of this instrument, and those of a very com- 

 plete Wheatstone bridge arrangement, which may be deemed 

 satisfactory. 



given in the Table for that purpose. The following is an instance of its applica- 

 tion, in which V = 127 and V 41 volumes. 



log. 877-975 

 + log. 127 



- log. 41 



log. 2719-518 = 

 + 101-80877 



2-9434822 

 2-1038037 



5-0472859 

 1-6127839 



3-4345020 



log. 2821 -32677-7-2 = )3j4504f>3jl 



log. 53-11616 1-7252267 



9-0960553 



log. 44-0201047x2= T6436510 



2 



log. 1937-7 

 274 



= 3-2873020 



16637 = 1664 Centigrade nearly. 



The resistance of 17 units in the voltameter is made of German silver wire, so 

 that the variation of its resistance with that of atmospheric temperature shall he 

 so small as not to affect the correctness of calculated results. 



VOL. II. N 



