TRANSACTIONS OF SECTION A. 343 



in the solar spectrum, using Abney's wave lengths, corrected to accord with 

 modern values, as the standards. 



The wave lengths obtained are probably correct within one unit. Better 

 results could be obtained with a grating, but very prolonged exposures would 

 be required. 



In the preparation of the emulsion Abney's prescription was generally fol- 

 lowed, with some modifications in detail found advantageous in practice. A 

 full description of the method of preparing such an emulsion with ease and cer- 

 tainty will be given in another place. 



i. The Specific Heats at High Temperatures and the Latent Heals oj 

 Metals. By H. C. Greenwood, M.Sc. 



Part L ALtrarNiTTM and Zinc. 



This investigation was undertaken to provide more reliable data for the 

 specific heats of metals at high' temperatures than those at present available, 

 particularly in the region of their melting-points, and also to determine the 

 latent heats of fusion. The metals studied in the first stage were aluminium 

 and zinc, on account of their comparatively low melting-points. In both cases 

 the published data were very unsatisfactory. In order to carry out experiments 

 above the melting-point the metals were sealed up in silica tubes, which were 

 dropped, not directly into the calorimeter water, but into a funnel-shaped tube 

 filled with light calcined magnesia. As the use of this entails a comparatively 

 long intervals before thermal equilibrium is attained, special precautions were 

 necessary to ensure maximum regularity and constancy in the cooling and heat- 

 ing conditions. Special attention was also devoted to an automatic arrangement 

 for swinging round the furnaces over the calorimeter and dropping the specimen 

 at the desired moment by the fusion of a platinum suspension loop. The fur- 

 nace only approached the calorimeter iust before dropping the specimen and at 

 once returned to its original position. In this way the transfer of heat from 

 the furnace to the calorimeter was rendered negligibly small and any radiation 

 from the furnace was the same during the initial and final periods. Consider- 

 able difficulty was experienced in making up the specimens from the cracking 

 of the silica envelopes as the metal inside expanded and contracted. Finally, 

 however, by careful manipulation it was found possible to overcome the diffi- 

 culty. The specific heat of fused silica being unknown it was necessary in the 

 first place carefully to determine this, as the thermal equivalent of the silica 

 envelope was a considerable fraction of the whole. This was the more neces- 

 sary as the temperature coefficient of silica is fairly large. The curve for the 

 mean specific heat of zinc was found to be continuous above and below the 

 melting-point, while the latent heat of fusion was found to be about 26 gr. cals. 

 per gram. In the case of aluminium the curve exhibited a sharp upward bend 

 just below the melting-point, which is probably to be associated with a prema- 

 ture fusion of the metal. By including this heat evolution the latent heat was 

 found to be about 95 gr. cals. per gram. The curve for the specific heat above 

 the melting-point was found to be steeper than immediately below. 



5. On the Recent Eclipse. By Kev. A. L. Cortie, S.J. 



6. On the Recent Eclipse. By J. H. Worthington. 



