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the subject earnestly, having addressed the Board of Trade (in
July, 1889) with a view to (1) providing a trustworthy standard
of light (2) prescribing a standard photometer with which all
official photometers should be compared, and (3) giving legal
force to tests made with a portable photometer; the reasons for
which are fully set out in the Committee's communication. No
action appears to have been taken in the matter at present by the
Board of Trade.
2. As regards Purity. The gas was free from sulphuretted
hydrogen throughout the year; and the quarterly average
quantity of other sulphur compounds present in the gas, was considerably
less than the quantity permitted; the maximum, moreover,
not having been attained on any occasion. But, as will be
seen in the following table, the maximum, the minimum, and the
average amounts actually found in 1890, considerably exceeded
the proportions in 1889, as these exceeded those found in
1888.

Ammonia, a valuable residual product of gas manufacture,
was present in the gas more or less frequently throughout the
year, but only in slight quantities. On no occasion was the limit
fixed by the Acts of Parliaments—viz., four grains in 100 feet
of gas—exceeded.