46. Similarly we have, 
(a) 6A. p.S(q Kq,) S(r Kr,) =Uline in space ( p, q, 7) perpendic- 
ular to plane (q,, 7;)- 
This line is therefore— A,.q,.Kr,.[A.p.Kq.7r],, the constant factor 
being determined by putting p, q, r=1, j, k, 91,71 J, k&. This beeomes, to the 
factor Sr K7,, the line of 44 (a) when r, is perpendicular to the plane (p, q) 
(b). 6 A.S(pKp,)S8(qKq)S(r Kr) 
== S8oA.piIeQut K, Aye, ology sis 
= product of volumes times cosine of angle between the spaces of the parallelo- 
pipeds (p, 9, 7), (Pi, diy 71) 
(ce). 24A.pS(q Kq,)S (7 K1r,) S(s Ks,) =line perpendicular to 
Cis Gis Tr) Ay Dae Gy Ty SPE p. 
This becomes, to the factor S (s A’s,), the line (a) when s, | (p,q, 7). 
(4). 244.S(pKp,) S(qKq,) S(r Kry), S(s Ky) 
—=Sp’ Kp. p’, K p, =product of scalar contents of 
(P, 9% Ts 8)y (Ps G19 Try 81): 
47. We have given sufticient illustrations of the value of alternate processes. 
The symmetric processes are capable of similar development although we have 
scarcely touched upon them. 
A New Form or GALVANOMETER. By J. Henry LENDI. 
The galvanometer which I am about to describe is a result of the 
difficulties experienced in attempting to make use of several very sensitive 
galvanometers in the physical laboratory of the Rose Polytechnic Institute. 
These difficulties are due to local changes in the earth’s magnetic field, 
arising from moving locomotives, electric motors and street cars in the 
neighborhood of the laboratory. It will be seen that the existing condi- 
tions are anything but favorable to the use of a very sensitive galvanom- 
eter depending on the earth’s field for the directive force. 
In the past year or two several attempts have been made to overcome 
this difficulty by making a galyanometer of the D’Arsonval type; that is, 
one in which the directive force is independent of the earth’s field. This 
galvanometer differed only from the ordinary D’Arsonval instrument in 
that the field was excited by an auxiliary battery instead of a permanent 
magnet. By this means we were able to secure a very intense controlling 
field, and thereby, thought we should be able to make a galyanometer 
