O. Harger—New North American Myriopods. 117 
W.J. M. Rankine on the General Law of the Transformation of 
Energy, Phil. Mag., 1858. 
In fi if we suppose that the electro-magnetic engine 
does work, the strength of the current will fall in passing from 
the resistance O C to O D, by reason of the counteractive force, 
to the lower isoelectric curve ab; and a’abb' a’ will represent 
the cycle of operations gone through by the performance of 
work and a return to the condition of an idle battery. 
In fig. 2 a= ees In thermo-dynamics a represents the 
elasticity of a gas whose volume is represented by the line R. 
n electro-dynamies a may be taken to represent the capacity 
of a circuit, of given resistance, for work. 
ne area of the figure ab’ a’ represents the work accom- 
plished in going through the cycle of operations abb’a'a. As 
in thermo-dynamies we shall have Q’—Q= A F, where F repre- 
Sents the area abb’a’ and Q and Q’ the distribution of tensions. 
When the area F becomes infinitely small we have d(Q= AdF, 
and by a discussion of this area in reference to a change from 
m to dm it is found that —< constant. 
_ tn an electric circuit if T—2 represents the difference of poten- - 
th ~ any two points, then we have Heat = Q’ (T'—?) or 
a y 
bg Q’=a constant for any one epoch, and m may be taken 
‘0 represent T—¢ The remarkable fact that the efficiency of 
e 
. 
both the thermo-dynamic and electro-dynamic engine is ex- 
Pressed by the same function ot has already been noticed by 
Mr. J. P. J oule, Manchester Transactions, vol. x. 
en 
Arr, XXL Brief Contributions to Zoilo the Mi 
Mahed gy, from the Museum of 
Fale College, No. XXIU.—Descriptions of New North Amer- 
can Myriopods ; by O. HarGeEr. 
ai Museum has lately received a number of interesting 
b Ynopods from various parts of the country, collected in part 
4 the writer while traveling across the continent as a member 
e f. Marsh’s Geological Expedition to the Rocky Mountains 
mn ific Coast. i t 
weg by entomologists, a large proportion of these species are 
and’ and in the following article a few of the most interesting 
“~~ Characteristic forms are described. 
