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LEWIS EVANS—ADDKESS : 
with a piece of sand-paper were sold for Is. The ordinary match 
followed in 1833, and the safety-match in 1855. As for lamps, the 
old cruse form was giving way to the Argand lamp invented in 1784, 
when, in 1800, Carcel in France introduced a pump-lamp, which 
in 1836 was superseded by the Moderator; hut as late as 1811 the 
Eddystone Lighthouse was only illuminated by 24 wax candles. 
Petroleum was not used for lighting until 1855, and its use did not 
become general until the introduction of the duplex lamp a dozen 
years later. Coal gas had first been used for lighting a building in 
1787 by Lord Dundonald, who used it occasionally for lighting Culross 
Abbey, and in 1797 Murdock had lit Boulton & Watt’s works by it. 
In 1803 the Lyceum was lit, and in 1810 the Gas Light & Coke 
Company was started. By 1816 gas was in general use throughout 
London. Coal gas is still the chief source of artificial light, having 
found a useful auxiliary in the incandescent mantles introduced of 
late years, and well known by the name of Welsbach, though their 
cost and price have yet to be more nearly reconciled. Another 
comparatively new gaseous illuminant is acetylene gas, which was 
introduced about five years ago; being easily made from carbide 
of calcium, and affording a most brilliant light, it may have an 
equally brilliant future before it. 
Another matter in which chemistry has greatly benefited man¬ 
kind is photography. The effect of light on silver salts had been 
noticed by Scheele about 1770, and in 1802 Wedgwood succeeded in 
making photographs with nitrate of silver, but failed to fix them, 
and it was not until nearly 1830 that J. N. de Niepce made a suc¬ 
cessful permanent photograph; in 1835 Eox Talbot devised his 
method of photographing on paper, and this was published in 1839, 
just before the publication of the Daguerre and Niepce improved 
method for photographing on silver; in 1850 the use of a film of 
collodion on glass was introduced by Archer at the suggestion of 
Le Gray; in 1856 came Norris’ dry plates, improved by Savce & 
Bolton in 1864 ; and gelatine dry plates were introduced in 1888. 
Amongst the many uses of modern photography to science besides 
the preparation of photographic blocks accurately depicting natural 
objects, and the production of true magic-lantern slides, mention 
must be made of stellar photography, by which exact star maps 
are made and new planets discovered; microphotography for 
recording the discoveries made by the microscope ; and telephoto¬ 
graphy for showing objects as seen through a telescope. In these 
days the aid of chemistry is sought by nearly all the industries of 
the world, and applied chemistry each year occupies a more im¬ 
portant position in commerce. At the same time fresh discoveries 
