120 
POPULAE SCIENCE REVIEW. 
journals) in their possession. And if they do know of such persons. I ask 
them on behalf of science, of my fellow-observers, and on my own behalf, to 
use every effort to secure their assistance, and to favour me with their names 
and addresses. We want old records, we want records for the present year, 
and from many parts of the country we want returns for the future, if a few 
persons will notify to me their willingness to assist, and to pay 10s. 6d. for 
the very cheap and simple gauge now supplied. To prevent needless corre- 
spondence, I annex a list of the places in Middlesex whence returns have 
been already collected for the years mentioned in the last column, and shall 
be very glad of any additions or corrections. Other counties, or the complete 
list for the whole country, shall be sent to any one willing to make good use 
of it. I may add that an influential committee of the British Association 
has been appointed to superintend and assist in my investigations, and that 
they cordially support my present application. The committee is composed 
of J. Glaisher, Esq., F.R.S., Lord Wrottesly, F.R.S., Prof. Phillips, F.R.S., 
Prof. Tyndall, F.R.S., Dr. Lee, F.R.S., J. F. Bateman, Esq., F.R.S., R. W. 
Mylne, Esq., F.R.S. and Mr. J. Symons.” 
METALLURGY, MINERALOGY, AND MINING. 
The determination of the Percentage of Mine-Gas in any mixture can be 
accomplished with accuracy by means of an ingenious instrument, which has 
been devised by Mr. Ansell. The apparatus, when complete, is not larger 
than an old-fashioned watch, and may with convenience be carried by mine 
overseers into the gallery of mines. It consists of a small aneroid barometer, 
the case of which is made perfectly air-tight, but the interior of which may 
be placed in communication with the external air by opening a small screw 
fastened on the handle. The brass back of the barometer is replaced by a 
thin plate of porous earthenware, and may be covered with a brass cap or 
back placed on a hinge like that of a watch. Under ordinary circumstances 
the screw remains open, but when it is required to test the gas in a mine, the 
screw is closed and the cap removed from the porous plate. Immediately 
diffusion takes place, and the pressure increasing, causes a corresponding 
movement of the hand of the barometer. In about 45 seconds the maximum 
effect is produced, when the position of the hand indicates, by means of a 
vernier, the percentage of mine-gas present. If the apparatus be left for a 
sufficient time, the internal pressure forces the excess of gas through the 
porous plate, and the needle returns to the zero point. On subsequently 
allowing diffusion to take place into pure air, the index retrogrades to the 
same extent (if the mixture does not contain more than 10 per cent, of mine- 
gas or “ fire-damp ” to which it had previously advanced. — Yide Chemical 
News , Dec. 15. 
A new Iron Ore is described by Mr. John Sutherland, of Glasgow. It 
has much of the characteristic appearance of plumbago, and leaves a black, 
