604 
in the human body. The subject was con- 
fined in a room whose walls consisted of a 
layer of copper, outside of which were one 
layer of zine and three layers of wood, with 
air spaces between. The temperature of 
the air spaces was kept the same as that of 
the inclosed room, by means of currents of 
air. The condition of uniformity of tem- 
perature was tested by many thermo-elec- 
tric junctions in series, which were distri- 
buted over the surface as uniformly as 
possible. The average position of the gal- 
vanometer mirror was kept zero. A de- 
flection of one millimeter on the scale cor- 
responded to one one-hundredth of a de- 
gree Centigrade. The amount of heat 
evolved in the room was calculated from 
the corresponding mass and change of tem- 
perature of the air which was forced to 
enter and leave the room through pipes. 
Frequent analyses of the air were made to 
determine carbon-dioxide and water vapor. 
The average of the results indicated that 
the law of conservation of energy was true. 
Professor E. B. Rosa read a paper by him- 
self and Mr. A. W. Smith, on electrical res- 
onance and dielectric hysteresis. The 
dielectric experimented on was used_in the 
form of a condenser, which was placed in 
an electric circuit, in series with a coil 
whose self-inductance was just sufficient to 
bring the alternating current used into 
phase with the HE. M. F. The power ex- 
pended in the circuit was made up of two 
parts, one proportional to the resistance of 
the coil, and the other proportional to the 
equivalent resistance of the condenser. 
These quantities multiplied by the square of 
the current (virtual) gave the power ex- 
pended. 
Dr. Margaret E. Maltby presented an in- 
teresting paper on a method for the deter- 
mination of the period of electrical oscilla- 
tions and some applications of the same, 
which was based upon a new application of 
the Wheatstone bridge principle. The two 
SCIENCE. 
[N. S. Von. VI. No. 148. 
halves of the measuring instrument—an 
electrometer—serve as two arms of the 
bridge, and the other two contain a con- 
denser joined to the electrometer needle 
and the two pairs of quadrants respec- 
tively. The relation that exists between 
these two, when there is no deflection, 
is a function of the rate of alternations in 
the current that passes through the sys- 
tem, viz: 7=xzCR, when Tis the period 
of a single alternation, C the capacity 
and & the resistance. If C is known in 
electrostatic units and / in electromagnetic 
units, C/v* should be substituted for Cabove, 
and it is then possible to solve for v. Other 
applications of the method are evident. 
See Wiedemann’s Annalen, B. 61, H. 3, 
8. 553. 
In a joint session of Sections A and B 
Professor G. W. Patterson, Jr., read a pa- 
per on the electro-static capacity of a two- 
wire cable, in which he deduced the formula. 
0.01206 A 
we SRD ED FD 
~ JER D+ D?—D 
when Cis the capacity in microfarads per 
kilometer, K the dielectric constant of the 
medium, & the radius of each conductor 
and D the least distance between them. 
Common logarithms are used. Professor 
W.F. Durand explained an approximate 
method of treating differential equations, 
in which he integrated by summing up 
areas considered as trapezoids. By making 
the intervals small enough any degree of 
accuracy might be obtained. Professor 
Alexander Macfarlane explained a new 
method of solving certain differential equa- 
tions that occur in mathematical physics. 
The method was applied to equations whose 
solutions involved exponential and sine 
functions. Mr. C. P. Steinmetz was on the 
program to read a paper on the screening 
effect of induced currents in solid magnetic 
bodies in an alternating field; but, much to 
