22 Dr. Playfair’s Lecture on the Great Exhibition of 1851. 
viously could not be done generally effects a moral as well as a 
physical result. The communication of a new power often oc- 
casions great social changes. It has been ak! said, that the 
discovery of the Greek fire projected from the walls of Constan- 
tinople “saved Europe from desolation by rhe Saracens ;” and 
it is equally true, that the personal animosity of warriors and the 
hostile spirit of nations have been much subdued by the new 
system of tactics introduced when a German monk, in deflagra- 
ting a mixture of sulphur, nitre, and charcoal, discovered gunpow- 
der. Morality was improved and crime lessened, when the bril- 
liant lighting of our streets by the ebaasetor of gas made every 
passer-by a detective policeman ; just as the cares, anxieties, and 
expenses of a government, will be dnniishedd by a fuller devel- 
opment of the electric telegraph. 
In addition to the direct communication of power, the increas- 
ed economy of time resulting from chemical appliances is of im- 
ense importance in manufactures. ‘This sometimes follows the 
discovery of new bodies endowed with peculiar properties, but it 
far more commonly arises from the reduction of a complex to a 
simple process. It is with chemistry as with mechanics ; the pro- 
ress of discovery is in the direction of simplification. The sim- 
plification of complex processes is the economy of labor, the hus- 
banding of wealth. Industry, in its progress, continually finds 
more ready means of cultivating and reaping’ fields long in its 
Foti ti’s house, containing a litter of young pigs, wa: s burned to 
the ground, it was natural that he should discover he delicate 
taste of roasted pig ; and it was equally natural, asa consequence 
of this discovery, that the inhabitants of Pekin should introduce 
pigs into their houses, and burn them down, when they desired 
useful and seemingly the most obvious arts make their way 
among mankind.” ‘The moral of this well-known story is of 
every day occurrence in the chemistry of the arts. Nota year 
s without the most mature processes of manufacture being 
further simplified and economized. It is with industry as with 
nature; many of the lower animals have a repetition of organs, 
destined for the performance of similar functions exercised by 
single organs in the higher animals. Various stomachs and sev- 
eral eyes in the lower creatures are not more effective than one 
stomach and two eyes in man. The law of repetition of organs 
is like the complex ‘processes of manufactures, represented by 
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