366 



MR. P. O. PEDERSEN ON THE SURFACE-TENSION OP UQUIDS 



of which is somewhat smaller than the smallest radius of the curvature of the aperture. 

 On the drawing is constructed the curve abed, described by the centre of a circle with 

 radius r rolling inside the curve ABCD. The values of the radius vector for the 

 curve abed corresponding to <f) = 0, 6, 12, &c., are determined on the drawing. By 



Fig. 9. 



help of these values and by using a small milling machine, with the above-mentioned 

 little file as cutter, the orifice can be cut in the correct form ABCD. Further 

 particulars are given in the original paper. 



The plate B is in most cases of platinum iridium (90 Pt+10 Ir) and has the form 



A 



B 



Fig. 10. 



of a circular plate, about 17 mm. in diameter and about 0'5 mm. thick. In the 

 middle of each plate the thickneas is reduced to about 0'25 mm. Fig. 10 shows the 

 ordinary arrangement of aperture and conducting tube. A represents a glass tube, 

 B a perforated plate, and C a ring of iudiarubber. Some few apertures are made in 



