2 GWYTHER, Modes of rupture of a liemispJierical sJiell. 



more specimens were tested. One specimen of each size 

 was reinforced at the base (la, 2a, 3a in the Table, p. 7). 

 The other specimens of each size were not reinforced 

 (marked i, 2, and 3 in the Table, p. 7). 



The several specimens and the results of the tests are 

 described below, but it appears best to state first the 

 general modes of rupture as the load increases. 



First. At some load a longitudinal crack develops 

 which extends gradually in the meridian plane. 

 There are several such cracks fairly regularly 

 distributed, but no doubt decided in position at 

 first by some accidental weakness. When once 

 started they doubtless affect the condition of the 

 specimen. 



In the specimens not reinforced at the base, 

 the cracks started at the base ; in those which 

 were reinforced at the base they commenced 

 at the top. 

 Secondly. When the load was increased, and (except 

 in the case of the two smaller specimens) before 

 the longitudinal cracks had extended through the 

 material, rupture took place quite suddenly by a 

 fracture roughly along a parallel of latitude. 

 This fracture was approximately conical and 

 nearly normal to the spherical surfaces, although 

 in all cases the vertex of the cone appeared to 

 be in the axis slightly below the centre of the 

 sphere. 

 It must be understood that the fracture was irregular, 

 and that the description is of its general character, 



Description of tlie sped mens and their riiptnre. 

 The specimens were all of the same description of 

 concrete, and the difference between the radii of the 



