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I. RESEARCHES ON THE RESISTANCE OF VESSELS OF WROUGHT IRON TO COI

(Reprinted from the Transactions of the Royal Soc

THE following experiments were undertaker request of the Royal Society and the Britis for the Advancement of Science. Their ol termine the laws which govern the strength vessels exposed to a uniform external for immediate practical application in proportion curately the flues of boilers for raising stean hitherto been constructed on merely empiric

It is well known that the immense ext application of steam power, and the conseq ment to economise as far as possible the f for its production, together with the growing employ the expansive principle, has caused crease of the working pressure from 10 lbs. to even in some cases to 150 lbs. on the

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tunately, however, our knowledge of the principles of construction has not kept pace with our desire to economise, and hence the change has been accompanied by an increase of dangerous and fatal accidents from boiler explosions. Investigation has frequently shown these lamentable catastrophes to have arisen from ignorance of the immense elastic power of steam, and from a want of knowledge of the forms of construction best calculated to retain an agent of such potent force; and as explosions become more frequent in proportion as the pressure is increased, it is the more necessary to inquire into the causes of such disasters, and to apply such remedies as may effectually prevent them.

In order to save space, and to increase the generative powers of boilers, internal flues and tubes have been generally adopted, and that without sufficient attention to proportioning their diameter, length, and thickness of plates, so as to ensure safety on the one hand, and economy of material in its judicious distribution on the other. Hitherto it has been considered an undisputed axiom among practical engineers, that a cylindrical tube, such as a boiler-flue, when subjected to a uniform external pressure, was equally strong in every part, and that the length did not affect the strength of a tube so placed. But although this rule may be true when applied to tubes of indefinite length, or to tubes unsupported by rigid rings at the extremities, it is very far from true where the lengths are restricted within certain apparently constant limits, and where the ends are securely fastened in frames, which prevent their yielding to an external force.

In some experimental tests to prove the efficiency of some large boilers, the author had some misgivings as to the strength of the internal flues to resist a force tending to collapse them. In these experiments it was found that flues of 35 feet long were distorted with considerably less