160 Mr Buchanan on the Strength Materials. 
doubt of the results, to which we might then safely appeal as 
the standards of practice. It were much to be wished, therefore, 
that such experiments could be undertaken ; and the object is not 
unworthy of public support. The experiments, however, which 
have been already made are, so far as they go, highly valuable ; 
and ample information in regard to these, will be found in 
the work of Mr Barlow, already referred to, which contains, be- 
sides his own experiments, and those of several other observers, 
an abstract of those Buffon made on oak-timber, by order of 
the French Government, and which form by far the most exten- 
sive series, and the most satisfactory, yet performed ; an ac- 
count of an interesting set of experiments, made by Mr Telford 
on the cohesion of iron with a hydrostatic press and of ano- 
ther important series made by Captain Brown, R. N., with a 
power of compound levers, similar to that of the weighing ma- 
chine. Besides these, accurate experiments have been made by 
Mr George Rennie, on the strength of different materials, the 
results of which are contained in the Philosophical Transactions 
for the year 1818. Some observations have also been made b 
Mr Tredgold, on the deflection and transverse strength of cast- 
iron, the account of which was published in his useful work on 
that subject. 
In another Number of the Journal, I shall endeavour, from 
these different sources of information, to lay down a few simple 
rules for calculation, and to illustrate their application by a few 
examples, referring, in the mean time, to Profes sor Leslie’s Ele- 
ments of Natural Philosophy. I may now also state the results 
of some experiments made at the School of Arts here, with an 
apparatus which I had constructed for that useful institution. It 
consists of a cylindrical hydrostatic bellows, seventeen inches in 
diameter, which exerts various pressures, according to the force 
of water or air within it, and which was found, could be carried 
to the extent of 20001b., the pressure being measured by a mer- 
curial gauge. This instrument may be used in various ways ; but 
I found it most convenient to obtain the pressure, by exhausting 
the air from within the bellows by means of an air-pump, and al- 
lowing the external atmosphere to act on the top and sides. Two 
upright bars being then erected, one on each side of the frame of 
the bellows, the bar whose strength was to be measured, was sup- 
