47 
Note upon a Sliding-scale for correcting Barometer 
Readings to 32° Fah. and Mean Sea Level. 
By H. ©. Russert, B.A., F.R.A.S., Government Astronomer. 
[Read before the Royal Society of N.S. W., 1 September, 1880.] 
Just eleven years since I had the honour of reading before this 
- Society a description of the sliding-scale which I then designed 
and made for the purpose of doing away with the computation 
which had previously been necessary when the humidity of the air 
was required from readings of the dry and wet bulb thermo- 
meters. That sliding-scale has been a useful servant in Sydney 
and other observatories ever since, and has saved an amount of 
time which it would be difficult to estimate ; but it only met one 
temperature and altitude at one in: ion. 
The scale was made by taking a strip of paper and at one end 
—say Bathurst, 
and altitude ; the 0 of the scale was then placed on the table so 
