SECTIONAL TRANSACTIONS.— A. 323 



Friday, September 11. 



Presidential Address by Prof. A. Ferguson on Trends in modern physics 

 (10.0). 



In the course of the address the President remarked that, through the 

 kindness of Imperial Chemical Industries, Ltd., he had been able, in 

 collaboration with his colleague, Mr. Cockett, to obtain preliminary esti- 

 mates of the specific heat of heavy water at different temperatures. These 

 values were obtained by experiments made on a sample of 375 gm. of heavy 

 water of 99-2 per cent, purity, lent by Imperial Chemical Industries, Ltd. 

 The results, which are expressed in terms of the 20 calorie, are shown 

 in the table given below. It will be seen that the specific heat is 

 consistently higher than that of ordinary water, and that a minimum 

 is indicated at about 41° C. The results for ordinary water were obtained 

 by the same method as that used in the experiments on heavy water. 



Table. 



D 2 



1 oo9 

 ioo7 

 10054 

 1 0043 

 1 -003,5 

 1 ' oo3 

 i v oo3 s 



Discussion on Elastic and absorptive properties of fibres (11. 10). 



Dr. W. Astbury. — Elastic protein fibres. 



Certain natural protein fibres, in particular the hairs of mammals, are 

 endowed with long-range elastic properties recalling those of rubber. The 

 effect is shown by X-ray and related studies to be due to combinations of 

 polypeptide chain-molecules which are normally in a regularly folded con- 

 figuration, from which they may be pulled out straight by the application of 

 tension, and to which they return when the tension is released. By suitable 

 modification of the state of cross-linkage of these polypeptide chains both 

 the elastic range and the driving force of elastic recovery may be varied con- 

 siderably. Animal hairs, for instance, may actually be contracted to a length 

 only half their natural length. The chief muscle protein, myosin, both from 

 the X-ray and physical elastic point of view, is closely analogous to one 

 of the forms of the hair protein, keratin, and there is apparently some funda- 

 mental type of molecular fold common to both. The crystalline proteins, 

 which are built from ' globular ' molecules, have now also been shown to 

 be based on folded polypeptide chains. The latter are liberated from their 

 special configuration by the change known as ' denaturation,' the resulting 

 insoluble mass being often highly elastic like keratin and myosin. X-rays 

 show that this elasticity is again to be referred to groups of folded poly- 

 peptides which may be drawn out into straight chains just as keratin and 

 myosin may be so drawn out. By this means artificial protein fibres may 

 be prepared from originally globular molecules. 



The detailed interpretation of the deformation of folded protein chains and 

 their long-range elasticity presents one of the most difficult and fascinating 

 problems in molecular mechanics. 



