684 
Proceedings of the Royal Society 
An instrument, constructed according to the following description, 
promises to fulfil all the conditions mentioned in Professor Poynting’s 
circular. Its sensibility is amply up to the specified degree. It is, 
of necessity, largely influenced by temperature, and it is not certain 
that the allowance for temperature, or the means which may be 
worked out for bringing the instrument always to one temperature, 
may prove satisfactory. It is almost certain, although not quite 
certain, that the constancy of the latent zero of the spring will be 
sufficient, after the instrument has been kept for several weeks or 
months under the approximately constant stress under which it is 
to act in regular use. 
The instrument consists of a thin flat plate of springy German silver 
of the kind known as “doctor,” used for scraping the colour off the 
copper rollers in calico printing. The piece used was 7 5 centimetres 
long, and was cut to a breadth of about 2 centimetres. A brass weight 
of about 200 grammes was securely soldered to one end of it, and 
the spring was bent like the spring of a hanging bell, to such a 
shape that when held firmly by one end the spring stood out 
approximately in a straight line, having the weight at the other 
end. If the spring had no weight the curvature, when free from 
stress, must be in simple proportion to the distance along the curve 
from the end at which the weight is attached, in order that when 
held by one end it may be straightened by the weight fixed at the 
other end. 
The weight is about 2 per cent, heavier than that which would 
keep the spring straight when horizontal ; and the fixed end of it 
is so held that the spring stands, not horizontal, but inclined at a 
slope of about 1 in 5, with the weighted end above the level of the 
