224 MU W. PAIEBAIEN AND MR, T. TATE ON THE JIECHANICAL PROPERTIES 
the force requisite to produce rupture will be increased in consequence of the m-egulai 
form of th! line of fracture. These theoretical deductions have been coniimed by 
tplments made upon columns of iron, wood, bone, stone, and other maten^s. ^e 
results of the experiments here recorded, however, show that when the length of 
cylinder does not gieatly differ from three times its rachus, the resistance to a crus ^ 
force is pretty nearly a constant, viz. on an average 12-313 tons per squaie inch 
case of tojass, 14 227 tons in the case of green glass, and 13-84 tons - case ol 
crown-glass. But, according to Coulomb’s law, the cubes of flint-glass (theu leng hs 
being Lsiderably less than thr-ee times their 
high! powers of resistance than the cylinders ; this discrepancy is probably owing to the 
iniury which the glass had sustained in the process of cutting, an o e impel 
annealing of glass when cast in the form of cubes and cylinders. 
Section III.— EESISTANCE OE GLASS GLOBES AJsD CTLIXDEEb 
TO INTEENAL PEESSGEE. 
In the following experiments it has been sought not only to detei mine the 1 
resistance to internal pressure, which is already well known ftom 
tions but to ascertain the direct tensile strength of the glass (of which - 
;Zre is a function) by a method free from many of the objections to " 
in Section I. The bursting pressure of cylindrical and spherical i esse 
to be in the ratio of the tenacity of the material, other things being the 
determination of the tensile strength upon this principle presents “ J ; 
peculiar advantages. As glass can be obtained in tolerably perfect sphei s, aM as the 
fracture of these may be effected by a uniform water pressure, incieas ^ ^ ^ 
Lmlarly without vibration, there is a better chance of ascertaining the ultmiate resis,- 
anh of the material, from the absence of those shoeks 
parable from any process depending upon the piling up o u eig , 
“it mtLg these experiments, a number of glass globes wei. promired of vm-yhig size 
and thickness. The stems were then flanched out by the blowpipe 
(fig. 6), and the diameter having been carefully measured, t my weie 
ready for experiment. To effect their rupture, each globe, k (hg. / j, 
was attached by means of a stuffing-box {a) to the cover of a stioiio 
wrought-iron boiler B, and was enclosed by the iron cylindrical vessel 
d to prevent the dispersion of the fragments when riiptiiie too v P 
In the stuffing-box the flanch of the stem of the globe was bed ec 
upon vulcanized india-rubber, in such a manner as to secure a water- ^ 
tight attachment without impeding the access of the water to re in elioi J 
tL boiler was connected with a hydraulic pump by means of the pipe i and ac 
gauge of the Schaeffer construction was flxed to the boiler to -S- - ‘ ^ P" 
With this arrangement it will be seen that as the pumping u as con i 
