45 



Assuming that the friction between two sections of the 

 wire is proportional to their relative velocity, a hypothesis 

 which accounts well for certain phenomena in sound, 

 I worked out its effect in this case, but the result failed to 

 account for the foots. This should not be surprising, for 

 though this assumption may be true or nearly so for small 

 relative velocities, it may well fail here when they are large. 

 The discrepancy may perhaps be attributed to the fact that 

 a strain which a wire will stand a short time, will ultimately 

 break it, and possibly in part to want of rigidity in the 

 supports of the upper clamp, both of which would favour 

 the heavy weight. 



I think we may conclude from the above considerations 

 and rough experiments, 



1st. That if any physical cause increase the tenacity of 

 of w^re, but increase the product of its elasticity and linear 

 density in a more than duplicate ratio, it will render it more 

 liable to break under a blow. 



2nd. That the breaking of wire under a blow depends 

 intimately on the length of the wire, its support, and the 

 method of applying the blow. 



3rd. That in cases such as surges on chains, etc., the effect 

 depends more on the velocity than on the momentum or vis 

 viva of the surge. 



4th. That it is very rash to generalize from observations 

 on the breaking of structures by a blow in one case to 

 others even nearly allied, without carefully considering all 

 the details. 



" Observations upon the National Characteristics of 

 Skulls," by S. M. Bradley, F.RC.S., Lecturer on Compara- 

 tive Anatomy, Eoyal School of Anatomy and Surgery, 

 Manchester. Communicated by Professor H. E. RoscoE, 

 F.KS. • 



The object of this paper was to show that the classification 

 at present in vogue, which arranges the crania of different 

 nations into four groups, viz., 1, dolicocephalic-orthognathic; 

 2, dolicocephalic-prognathic ; 3, brachycephalic-orthogna- 



