340 
POPULAR SCIENCE REVIEW. 
he breathes, and shuts out that oxygen which is more necessary 
to his life than even the warmth of his body. So terrible is 
the effect of atmospheric poison on his body, that when the 
cold comes, it finds more victims among the overcrowded 
homes of the poor than among any other class. Thus one 
week^s continuous cold — the thermometer ranging from ten 
to twenty degrees below the freezing-point during the second 
week of January in this year — added nearly 2,000 victims 
above the average deaths of the season of the year to the 
mortality of London. This (C wave of cold 33 was felt more 
acutely in that class of our metropolitan population whose 
systems are rendered less able to resist the influence of cold 
in attempts to secure warmth by the exclusion of fresh air. 
The materials of clothing used by man are obtained from 
both the animal and vegetable kingdoms. Types of the 
substances obtained for clothing purposes from the vegetable 
kingdom are afforded in cotton and linen. Cotton is the hair 
of a plant, obtained from the inside of the fruit. By the 
accident of a twist during its growth it is possible to spin it 
into a thread, and it thus becomes the basis of our great cotton 
and muslin manufactures. The fibres of linen are the vascular 
tissue of the common flax, which, when prepared, are formed 
into threads, which are woven into the textile fabrics known 
as linen. These materials are bad conductors of heat. It is 
on this account that they are used for clothing purposes. 
Where the object of dress is to keep in warmth, those sub- 
stances form the best articles of dress which conduct heat 
least. Another . class of substances used for dress are the 
hairs and fibres of animals. The wool of the sheep, and the 
silk produced by the silkworm, are the substances most con- 
stantly woven into the articles of dress. Both wool and silk 
are worse conductors than cotton or linen. Hence we find 
that animal substances are preferred to vegetable substances, 
when the object is to keep in warmth. 
It is, in fact, practically known that cotton and linen are 
cooler than cloth or silk : and whilst in this country we 
prefer the latter in winter, we have recourse to the former in 
summer. Men clothe themselves in winter with great coats of 
cloth, but they wear cotton and linen jackets in summer. 
In the winter, women clothe themselves with cloth mantles, 
but in the summer they put on their muslin, calico, and other 
light dresses. This is quite correct, and it should be recollected 
as a rule that cotton and linen garments are coolest, the 
linen being cooler than the cotton, and that woollen and silken 
garments are warmest. 
The colour of our clothes is not altogether a matter of 
indifference. White and light-coloured clothes reflect the 
