Chemistry and Physics. 141 
sisting of a wire of great conductivity and carefully insulated 
from the earth, except at the two grounds. By exploring the 
coast of France, two points on two surface lines not at the same 
potential could be found; and by means of a telephone of low 
resisterice, the Morse signals sent from Nova Scotia to Florida 
could be heard in France. Theoretically this is possible; but 
eked dklty: with the light of our present knowledge, the expen- 
diture of energy on the dynamo-electric engines would seem to 
be enormous. 
The points made in this paper are as follow 
1. Disturbances in telephonic circuits anally attributed to 
effects of induction are, in general, due to contiguous grounds 
of battery side A return wire is the only way to obviate 
these disturbance 
well- defined equipotential surfaces in the neighbor- 
hood of battery grounds shows the theoretical possibility of 
sat re hon across large bodies of water without the employ- 
ent and leads us to greatly extend the practical 
limit set by Stoinhel l. 
3. Earth currents have an intermittent character, with peri- 
ods of maxima and minima which may occur several times 
a minute during the entire day. This intermittent character is 
got absent. 
ysical Laboratory, Harvard University. 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND PHysIcs. 
1. On Chemical Curves as Lecture-Illustrations.—The gro 
ing importance of chemical dynamics renders it very desirable to 
use the graphical method in class instruction. In order to make 
clear the significance of these curves, especially to those who 
grasp se aa methods difficultly, Mrs has contrived an appa- 
glass cylinders, filled with water and inverted each in a circular 
glass trough, also containing water. Behind these + pears: is a 
corresponding series of glass tubulated retorts, of 100 c. c. capac- 
ity, each beak sa beneath the mouth of a cylinder. Provis- 
ion is made for mem off the overflowed water.. The frame of 
the author’s apparatus is 289 cm. long and 51 high, the capacity 
of each cylinder being about 270 ¢.c. To show the effect of dilu- 
tion upon the action of hydrogen sulphate upon zine, the sheet 
metal 0°55 mm. thick was cut into pieces 14 mm. square pre es 
and rolled into a T— The sulphuric acid, of specific gravity 
1843, was diluted to strengths varying progressively a 3 per 
