OF ARTS AND SCIENCES: FEBRUARY 14, 1865. 407 



Two experiments were made by Hodgkinson on pillars with the 

 pressure applied at intermediate points, between the centre and cir- 

 cumference. When the pressure was applied parallel to the axis, and 

 half-way between the axis and one side, the breaking weight was about 

 54 per cent of the breaking weight of a pillar of the same dimensions 

 with the ends rounded, so that the pressure was applied at the axis. 

 In another experiment, the pressure was applied at one eighth of the 

 diameter from one side ; in this case, the breaking weight was about 

 61 per cent of that of a pillar of the same dimensions with rounded 

 ends. In two experiments the pressure was applied in the direction of 

 a diagonal ; in both cases the breaking weight was nearly the same as 

 for pillars of the same dimensions with rounded ends. A few experi- 

 ments were also made on pillars with rounded ends, and other forms 

 than cylindrical. Square pillars had an average breaking weight about 

 58 per cent greater than cylindrical pillars of diameters equal to the 

 sides of the squares. The square pillars generally failed in the direc- 

 tion of the diagonals. A pillar of the section -4", 90.75 inches long, 3 

 inches across, and the ribs 0.48 inch thick, had a breaking weight 63 

 per cent greater than the computed breaking weight of a solid cylin- 

 drical pillar of the same weight and length. A hollow cylindrical pil- 

 lar of the same weight and length, and of an external diameter equal 

 to the width of the -|-, has a computed breaking weight about double 

 that found by experiment for the form +. A pillar of the section H, 

 3 inches in height and 2.5 inches in width, of the same length and 

 nearly the same sectional area as the preceding, had a breaking weight 

 about 2.6 times the computed breaking weight of a solid cylindrical 

 pillar of the same weight and length. A hollow pillar, 3 inches in 

 external diameter, and of the same weight and length, has a computed 

 breaking weight about 19 per cent greater than was found by experi- 

 ment for the pillar of H section. 



Several pillars, larger in the middle than at the ends, were tested 

 for the purpose of determining the most economical form ; the experi- 

 ments were not sufficiently numerous or varied to permit any definite 

 conclusions to be drawn. It would appear, however, that in pillars 

 with rounded ends there is a distinct advantage in making them some- 

 what larger in the middle than at the ends ; that is to say, a pillar may 

 be made of this form which would have a breaking weight greater than 

 a cylindrical pillar of the same weight. In pillars with flat ends there 

 is less advantage in departing from the cylindrical form. Hodgkinson 



