180 
sible that sufficient vapour or gas should condense on the surface of the balance to 
be instantly driven off by the warmth of the finger, with recoil enough to drive 
backwards a heavy piece of metal. 
Since these experiments were made, Mr. Crookes has examined more fully 
the action of radiation on black,and white surfaces.. At the highest exhaustion 
heat appears to act almost equally on white and lamp-blacked pith, repelling them 
in about the same degree. The action of light, however, is different ; these rays 
repel the black surface more energetically than they do the white surface. Taking 
advantage of this circumstance, Mr. Crookes has constructed an instrument which 
he calls a radiometer, very similar to those you see before you, except that instead 
of metal discs he used pith. This instrument rotates under the influence of both 
heat and light rays, the rapidity of rotation being in proportion to the intensity of 
the incident rays. 
At the close of the paper the instrument was further illustrated by experi- 
ments conducted by the rev, lecturer and by Mr. G. H. With. 
METEOROLOGICAL RECORDS FOR 1875 ; 
Being the Monthly Returns sent to the Hereford Times during that year. 
These Readings wre corrected for temperature and error of instrument, but they are not 
reduced to sea-level. The height of the barometer-cistern above sea-level is 187 feet. 
JANUARY. 
The mean of all the 9 a.m. barometrical readings for January is 29°673 
inches. 
The highest reading (30°427 inches) was registered on the 30th, and the 
lowest (28'873 inches) on the 24th. 
The mean temperature for January is, this year, 44°6 degrees, Mr. Glaisher’s 
average temperature for this month being 369 degrees. 
The highest reading of the thermometer in shade (55°8 degrees) was regis- 
tered on the 19th, and the lowest (30°1 degrees) on the 22nd. 
The mean degree of humidity for January, this year, is 89.9, complete 
saturation being 100. 
The rainfall amounts to 3°64 inches, the greatest fall in 24 hours (0°62 inch) 
occurring on the 23rd. 
There were 25 days on which 0°01 inch or more fell. 
The winds at 9 a.m. daily were as follows :—N. 0; N.E, 2; EH. 1; 8.E. 9; 
S. 10; S.W.6; W. 2; N.W. 1. 
: On the 24th there was a remarkable depression of the barometer, and a great 
gale of wind from W. and W.S. W., with vivid flashes of lightning during the night, 
