14 The Strength of Columns. 



Art. VI. — Sir William Thomsons Form of DanielV 

 Constant Battery. 



By F. J. PiRANi, Esq., M.A. 



[Eead 13th June, 1878.] 



Art. VII. — Tlie Strength of Columns. 

 By W. C. Kernot, M.A. 



[Read 13th June, 1878.] 



A COLUMN may be defined as a construction piece exposed to 

 a compression in one direction and otherwise unstrained. 

 Columns as thus defined are of constant occurrence in 

 engineering and architectural structures. About 50 per 

 cent, of the material in an ordinary roof or bridge truss con- 

 sists of columns ; the piston rod, connecting rod, and various 

 other important parts of a steam-engine perform the func- 

 tions of columns ; and immense quantities of cast-iron are 

 employed in the construction of warehouses, theatres, 

 churches, and other buildings in the form of columns. 

 The question of designing a column so as to secure 

 sufiicient strength at a minimum cost is therefore one of 

 vast practical importance. Columns vary much in size, 

 shape, and position, but, as a general rule, have one dimen- 

 sion considerably greater than either of the other two ; in 

 other words, they are comparatively long and slender pieces 

 of material. Further, they are usually, though not always, 

 straight. Bent columns, however, being of unfrequent 

 occurrence, will not be discussed in this paper. A column 

 is usually compressed in the direction of its length or greater 

 dimension, and it is immaterial, so far as strength is con- 

 cerned, whether this direction be vertical, horizontal, or 

 inclined. 



Columns are divided, according to their mode of fracture, 

 into two gi^eat classes. The first of these contains those 

 which fail by direct or simple crushing, unaccompanied by 



