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of Edinburgh, Session 1866 - 67 . 
acts only by its heat, but the exposed parts receive the peculiar 
influence of the light.” “ Among these parts,” he continues, “ we 
must certainly regard the eyes as not merely designed for the per- 
ception of colour and form. Their exquisite sensibility to light 
fits them peculiarly for transmitting it throughout the system, and 
we know that even a moderate light on the retina produces in seve- 
ral diseases a general exacerbation of symptoms.” 
If the light of day, then, contributes to the development of 
the human form, and lends its aid to art and nature in the cure of 
disease, it becomes a personal and national duty to construct 
our dwelling-houses, our schools, our workshops, our factories, our 
churches, our villages, towns, and cities upon such principles and 
in such styles of architecture as will allow the life-giving element 
to have the fullest and the freest entrance, and to chase from every 
crypt, and cell, and corner the elements of uncleanness and corrup- 
tion which have a vested interest in darkness. 
Although we have not visited the prisons and lazarettos of foreign 
countries, to describe the dungeons and caverns in which the vic- 
tims of despotism and crime are perishing without light and air, 
yet we have seen enough in our own country — in private houses, 
in the most magnificent of our castles, and in the most gorgeous of 
our palaces — to establish the fact that there is hardly a house in 
town or country without dark apartments which it is in the power 
of science to illuminate. In most of the principal cities of 
Europe, and in many of the finest towns of Italy, where external 
nature wears her brightest attire, there are streets and lanes in 
which the houses on one side are so near those on the other, that 
hundreds of thousands of human beings are neither supplied with 
light nor air, and carry on their trades in almost total darkness. 
Providence — more beneficent than man — has provided the means 
of lighting up to a certain extent the workman’s home, by the ex- 
panding power of the pupil of his eye, and by an increasing sen- 
sibility of his retina ; but the very exercise of such powers is pain- 
ful, and every attempt to see when seeing is an effort, or to read 
and work with a straining eye and an erring hand, is injurious to 
the organ of vision, and sooner or later must impair its powers. 
Thus, deprived of the light of day, thousands are compelled to carry 
on their trades principally by artificial light — by the consumption 
