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Art. XIII .- — On the Effects of Mildew on Canvas , and Notice 
of the Experiments of Mr Sanderson of Leith on this im- 
portant subject. 
1 HE damage sustained by canvas from mildew, is well known 
to all connected with the manufacture or use of that article. 
When canvas has been kept for any length of time in a place 
where it is exposed to the influence of damp, such as a store- 
house, cellar, or the hold of a vessel, and more especially when 
exposed to the continued influence of moisture, as in the part of 
a tent which is in contact with the ground, or when sails have 
been rolled up and stowed away in a wet state in stormy wea- 
ther, it becomes covered with mouldiness, spots of a dark colour 
appear in it, and it ultimately becomes rotten, so as no longer 
to be applicable to the purposes for which it was intended. The 
prevention of mildew and rot in sail and tent canvas, is a desi- 
deratum that has occupied the attrition and exercised the in- 
genuity of the manufacturer for more than half a century. The 
only methods hitherto employed have been the boiling and 
bleaching their yarns with alkalies. The disadvantages attend- 
ing these processes are very great : a considerable waste of the 
fabric, raw material and time, while the desired effect has been 
attained but in a ver}^ imperfect degree. Mr Sanderson of 
Leith professes to be in possession of a method which entirely 
supersedes the necessity of boiling and bleaching, and effectually 
prevents the baneful effects of mildew and rot, in sail and tent 
canvas, as well as in cloth of every description manufactured of 
hemp, flax, or even cotton. 
We need not insist in detail, upon all the advantages accruing 
from the preservation of this important article, as they will 
readily present themselves to every one who reflects upon the 
subject; but we shall offer a few remarks upon its great utility, 
in a national point of view. 
The injury done to canvas by mildew in the stores, even be- 
fore it is delivered out to the ship, is often very great ; and, in 
tropical climates, when the sails are furled up in a storm, or 
placed damp in the vessel’s hold, it is still greater. The injury 
done by a single wetting may often be estimated at one- fourth 
