ARTIFICIAL LIGHT. 89 
success ; but it is said that wood and peat gas are already used 
with great advantage in many German and Swiss towns. 
In addition to the contrivances adopted for obtaining 
artificial light already alluded to, and in common use through- 
out the civilized world, there are two others occasionally 
employed, although not yet produced on such a scale and at 
such a cost as to be economically important. One of these is 
merely a modification of ordinary gas-light, involving the use 
of pure oxygen gas, instead of atmospheric air, as the agent of 
combustion, and introducing a solid incandescent body, such as 
lime, to increase the intensity of the illuminating power. The 
other is the electric light, obtained by bringing into close 
proximity, without actual contact, two pencils of charcoal, 
and passing between them a powerful voltaic current. Great 
difficulty has been experienced in rendering light thus obtained 
sufficiently steady for any practical purposes, and these 
difficulties are not yet fully overcome, although a partial success 
has been obtained in Paris, by methods more simple and less 
costly than those before used. 
And now, in bringing to a close this account of Modern 
Illumination, let us consider for a moment bow far and in what 
way we are benefited by artificial light, rendered cheap and 
abundant by so many ingenious contrivances. 
Half a century ago, all the great capitals of Europe, although 
then not half their present size, were dangerous residences to 
them honest inhabitants, and unmanageable in regard to police 
supervision, owing to the difficulty of obtaining sufficient arti- 
ficial light during the long dark nights of winter. The growth 
of population that has since taken place, and the development 
of the resources of our own and other countries, would probably 
have been impossible, without the discovery and rapid intro- 
duction of some means of economically and effectually lighting 
the streets and alleys, which had long served as the haunts 
of thieves and dangerous characters of all kinds. It is not too 
much to say that, in this matter alone, the introduction of 
artificial light has been the main agent employed in effecting 
a social improvement, compared with which all others are 
secondary. The millions of cubic feet of gas now burnt nightly 
in our streets are, beyond comparison, the best, the most 
permanent, and the least expensive source of security that could 
have been introduced, and have served, more than anything 
else, to check those deeds of wrong and violence that darkness 
cannot fail to shelter, and invariably fosters. 
Nor are we less indebted to gas for lighting our public 
buildings of all kinds. Here, again, the necessity for increased 
light has enforced a consumption of material which, as far as 
we can see, no natural supply of oil and tallow could ever have 
