[smith] depression OF DISC UNDER PRESSURE 225 



The values of w have been calculated by this method for p equal 

 to 180, 350 and 550 mms. of mercury in the case of the diameters 

 already dealt with and the calculated values of w are compared in 

 Table IV with the corresponding readings of w obtained from the 

 curves on chart 1. It will be noted that the error in most cases is less 

 than one per cent, with two cases of two per cent, error and one case 

 of three per cent, error. 



A set of observations was also made for d equal to 5.16 centi- 

 metres for the purpose of further testing the formula. The values of 

 w obtained from the formula 1 and from the scale deflections are 

 given in the second and third columns respectively of Table V. 



It would, therefore, appear that the depression of the centre of a 

 disc under the arbitrary conditions laid down in the above experi- 

 ments is characterized by a mathematical relation much simpler than 

 the complicated nature of the differential equations of the theoretical 

 development would lead one to expect. However, it should be borne 

 in mind that the boundary conditions in the cases dealt with in these 

 experiments differ from the conditions usually treated, for not only is 

 the line of support during depression not at the edge of the disc but 

 it assumes different distances from the edge of the disc for the various 

 values of d. 



The effect of the rim beyond the the exposed area of the disc 

 must necessarily be considerable in these cases. It is intended at 

 some future date to see what influence this rim has on the depression 

 of the centre. 



In conclusion I wish to express my thanks to Professor I. F 

 Morrison and Professor A. E. Cameron of the University of Alberta 

 for tempering and preparing the steel disc for use in these experiments. 

 Also I desire to express my appreciation of the courtesy shown me 

 by the Associate Air Research Committee of Canada in permitting 

 me to present this paper. 



University of Alberta, 

 Edmonton. 



15— C 



