SCIENTIFIC SUMMARY. 
421 
white heat, and this specimen could not he forged at all. The conceivable 
causes of this difference were briefly discussed, such as the more or less 
complete removal of the occluded gases, changed state of combination of 
the phosphorus and sulphur, and melting out of phosphide of iron, leaving 
the metal porous. 
The Decomposition of Water . — A paper was read at the British Associa- 
tion, u On the Mutual Helpfulness of Chemical Affinity, Pleat and Electricity, 
in producing the Decomposition of Water,” by Dr. Gladstone and Mr. A. 
Tribe. Some metals are able of themselves to displace the hydrogen of 
pure water, while other metals are unable. Zinc, if perfectly pure, is in- 
capable of doing so; but if it be brought into contact with another metal 
still further removed from the power of effecting the decomposition of 
water, the electric force started by contact of the metals enhances the 
chemical affinity sufficiently to make it effective — or, otherwise expressed, 
the electrical tension, plus the chemical tension, upsets the state of equili- 
brium between the oxygen and the hydrogen. The amount of action may 
be measured by a Thompson’s galvanometer. The effect of varying the 
distance of two plates of zinc and copper was tried, and it was found that 
the chemical action increased slowly till the plates are within an inch or so 
of each other, but on continuing to bring them together the action increases 
at a rapidly accelerating ratio. Heat assists the action considerably. Mag- 
nesium is capable by itself of decomposing water, but its action is greatly 
increased by touching it with a piece of copper, and some of the hydrogen 
gas makes its appearance on the copper. If, instead of magnesium, a metal 
less capable than zinc of decomposing water be used, there is still found a 
deflection of the galvanometer, if it be united with a metal still more nega- 
tive. The order for pure water seems to be — platinum, silver, copper, iron, 
tin, lead, zinc, magnesium. 
The Quality of the Metropolitan Gas. — Dr. Letlieby, the chief Gas Ex- 
aminer appointed by the Board of Trade, has recently reported to the 
Corporation of the City, and to the Metropolitan Board of Works, on the 
quality of the gas supplied to the metropolis by the Cliartered, the Imperial, 
and the South Metropolitan Gas Companies, during the last three months ; 
from which it appears that the illuminating power has never been less than 
that required by the Act of Parliament. The common gas of the Chartered 
Company has ranged from an average power of 16*89 standard sperm candles 
at the Millbank testing-place, to 17*85 candles at the testing-place at Mile 
End. The Imperial Company’s gas has ranged from 15*72 candles at Cam- 
den Street, to 16*85 at Oakley Square, Chelsea ; and the gas of the South 
Metropolitan Company has averaged 15*78 candles. The cannel gas of the 
Chartered Company has had an average illuminating power of 25*74 candles 
at Millbank Street, and 26*06 candles at Arundel Street in the Haymarket. 
With respect to purity, Dr. Letheby reports that the gas at each of the 
testing-places has been constantly free from sulphuretted hydrogen, but that 
the fluctuation in the amounts of sulphur have been considerable, as from a 
minimum of 2*2 grains per 100 cubic feet of gas at Mile End, to a maximum 
of over 40 grains at Beckton, at Canuon Street, at Arundel Street, and at 
Hill Street, Beckham ; the average proportions at the different testing- 
places having been as follows : — The common gas of the Chartered Company 
