86 
NATURE 
[May 25, 1899 
the rudder head, the core which is sucked in depending, of 
course, upon the direction of the current received. Two rods, 
projecting above the surface of the water, receive the waves, and 
are in circuit with a coherer of special type, which affects a relay 
in the usual way. The actual processes involved in steering 
and controlling a torpedo are somewhat as follows. Let a 
torpedo, containing a suitable combination of the apparatus 
mentioned, be launched, say, froma vessel containing the neces- 
sary sending apparatus as described. Suppose the torpedo goes 
off its course. Then, by means of a switch an induction coil is 
circuit and allows the helm to fly back to the midship position. 
A large model of the apparatus has been constructed, and it is 
said to work with entire success under all kinds of conditions. 
THE Corporation of Bath have appropriated the necessary 
funds for the cost of tablets to be affixed to houses entitled to 
be considered as historic in their city. About forty tablets are 
to be put on houses which have been the homes of distinguished 
men, or are otherwise of historic interest, and the first of these, 
affixed to a house which was once the residence of Sir William 
Herschel, was officially unveiled on Apri? 
supplied with electric current, and waves or oscillations are 
These, on reaching the torpedo, pass into the pro- 
jecting wire, and thence reach the coherer. This operates 
An electric current 
now flows through a ‘‘ selector” to one of the solenoids, the 
iron core is sucked into right or left, and the helm is thus 
turned, 
generated. 
the relay, closing its secondary circuit. 
The vibration in the 
neighbourhood of the coherer restores it to the original resist- 
switch is opened and the waves cease. 
ance, the current passing through it becomes weaker and ceases 
to affect the relay coil, which therefore opens the secondary 
NO. 1543, VOL. 60] 
When the torpedo has attained a proper course, the | 
22 by Sir Robert Ball. The tablet is 
shown in the accompanying illustration, 
for which we are indebted to Sir Robert 
Ball. The inscription reads : ‘‘ Here lived 
William Herschel a.p. 1780.” In a little 
workshop at the end of the back garden 
of this house, Herschel made his New- 
tonian reflector, and it was from this spot 
that he discovered Uranus on March 31, 
1781. The Bath Corporation is acting 
wisely in taking steps to remind the 
citizens of the distinguished men who 
have lived within their boundary, and 
thus incidentally added to the reputation 
of the city. 
THE Physical Review (vol. viii. No. 3) 
contains an article, by Mr. J. G. McGregor, 
on the applicability of the dissociation 
theory to the electrolysis of aqueous solu- 
tions containing two electrolytes with a 
common ion. ‘The author calculates the 
theoretical relative amounts of the dis- 
tinctive ions transferred by the current, and 
compares them with observed values, for 
certain complex solutions. Another article, 
by Mr. J. O. Thompson, describes some ex- 
periments relating to the fatigue of metals- 
It was found by Lord Kelvin, in 1864, 
that a wire which had been kept vibrating 
for several hours or days, through a given 
range, and then left to itself, came to rest 
much quicker than when set into vibration 
after it had been for several days at rest. 
The present experiments are designed to 
prove that when temperature and initial 
amplitude of vibration are constant, and 
when the wire is not unduly loaded, the 
period and logarithmic decrement are also 
constant. 
AN investigation of 
mena by Mr. John Zeleny is also described 
at length in the Physical Review. The 
results show that during conduction 
through a gas under the influence of 
Rontgen rays, convection currents are produced in the gas, 
which in general move towards the electrodes. These currents 
| are caused by the motion of the free charges existing in the gas. 
| During the conduction, there is a rapid fall of potential within 
| o°1 mm. from the surface of the electrodes. By exposing the 
gas to Rontgen rays, the electric force acting 
Rontgen pheno- 
WEE, 
upon the electrodes 
is increased. 
| Mr. W. L. ScLaTEr, the director of the South African 
Museum, Capetown, is making arrangements for the preparation 
| of a series of handbooks on the zoology of the southern part of 
