SCIENTIFIC SUMMARY. 
521 
harmful. Dr. Hayes, however, has detected several cases of anomalous 
disease which could be traced to the habitual domestic employment of 
water so contaminated ; and it is, therefore, strongly advised that, before 
galvanized iron vessels are used for the water-supply of a house, it should 
be ascertained whether there is any chance of the metal being corroded 
and dissolved. 
It has long been a doubtful point whether carbonic oxide was really 
such a poisonous gas as some writers imagine. Although it is an almost 
invariable accompaniment of carbonic acid when produced by ordinary 
combustion, few persons have thought of ascribing to it a share in the 
calamitous results which have so frequently been caused by the inhalation 
of the vapours of burning charcoal. The lamentable accident at the 
Hartley Colliery first directed the attention of several physiologists to the 
subject, and the result has been that this gas must be now looked upon as 
a most violent and deadly poison ; common air, containing as small a 
proportion as one per cent., proving rapidly fatal to rabbits and other 
small animals, and a half per cent, killing small birds in a few minutes. 
The action of this gas on human beings has frequently been demonstrated. 
Sir Humphrey Davy, after three inspirations of the diluted gas, fell down 
senseless, and upon recovering from this, it was succeeded by giddiness, 
sickness, acute pains, and extreme debility, which lasted for some days. 
Since then, Mr. Wilter as nearly as possible killed himself by an inhala- 
tion of the pure gas. He fell upon the floor in a state of perfect insensi- 
bility resembling apoplexy, and with a pulse nearly extinct ; his life was 
only saved by his having pure oxygen gas forced into his lungs. On the 
Continent the employment of water-gas (a mixture of hydrogen with 
about thirty-four per cent, of carbonic oxide), as a means of illumination, 
has been forbidden by law, owing to the numerous fatal accidents which 
its escape into houses occasioned. These and several other instances, 
which have been collected together and examined by Dr. Letheby, prove 
without a doubt that the deadly properties of this gas have not been over- 
rated ; and as it has been also proved that this oxide is produced in the com- 
bustion of carbon whenever the supply of air is limited, — for instance, in 
brick-kilns, iron furnaces (about thirty persons having been poisoned at 
Clayton Moor from this cause), slow-combustion stoves, &c., — it is impor- 
tant that the public should be well acquainted with the very dangerous 
properties of a gas to which they are liable by many accidents to be 
exposed. 
An improvement in the oxy-liydrogen ' light has been effected by 
Mr. Fryer. The earth lime is generally employed as the incandescent 
body in this means of illumination ; but there are several objections 
to its use which render the discovery of a more efficient substitute 
advisable. Magnesia has been found to give the best results, as far as 
light is concerned ; but there was a difficulty in rendering it sufficiently 
coherent to resist the impact of the gases. After numerous experiments 
it was found that the best results were obtained by mixing together one 
part of sulphate of lime and two parts of calcined magnesia with water, 
moulding them into a cake and drying. The illuminating power, pressure 
and volume of gas being equal, is said to be exactly double that of lime. 
