95 
thermometers. No doubt when the ground is covered with 
snow the height at which the instruments are placed above 
it will cause differences. 
Unless the instruments are satisfactorily placed, the ob- 
servations with regard to moisture will be utterly unreliable. 
The 9 p.m. temperature observations and also the one at 
1 p.m. on the 10th of March, were taken from my rooms by 
means of an electrical arrangement which I have devised, 
and of which I have sent a fuller description to another 
Society, but I may say that the thermometer is a spiral 
metal thermometer which carries a finger. This thermo- 
meter was kept in the screen with the other instruments. 
I made the scale with a number of wires here uncovered, 
but elsewhere insulated, wound over a piece of ebonite, 
and the finger of the instrument is brought down upon 
these wires by two electro-magnets, and in my room, by 
a simple contrivance, I am able to tell which wire is 
touched by the finger. I have also arranged a hair hygro- 
meter to work in the same way, and intended to have 
both instruments working this winter, but through delays 
in getting the necessary material, and other causes, the 
winter caught me up, and when the weather was cold 
I was obliged to give up the idea of making changes * 
Consequently I used the thermometer, although being short 
of wire I only completed the scale to — 11 Cent., which 
is the reason why on many nights when the temperature 
fell below this I am unable to give any figures. 
The instrument which has been used many hundreds of 
times has turned out quite satisfactory, and I am sure that 
the principle can be applied to almost every instrument 
that carries a finger. The part of the hygrometer moved by 
the hair, for which I paid a long price to an incompetent 
* The instrument is only divided into | of a degree Centigrade, but 
I purpose making another in a few weeks divided to to of a degree. 
