Geological Society. 155 



the greater part of their physical behaviour isotopes are probably 

 also similar to one another; though, of course, their essential 

 differences in stability, which are usually placed amongst their 

 physical properties, are enormous. The question as to whether 

 their spectra will be identical, at present needs experimental 

 verification, If Dr. Soddy's expectation is fulfilled, a very 

 pregnant addition will have been made to our knowledge of the 

 connexion between spectra and atomic constitution. It is to 

 be hoped that Mine. Curie's investigation on the spectrum of 

 radium D (p. 31) will soon be completed. Mr. Aston's separation 

 of neon into two parts with atomic weights of 20 and 22 without 

 any difference in their spectra (p. 35), is in favour of Dr. Soddy's 

 expectation ; but it is not safe to generalize from this case 

 alone. 



The main part of this volume is concerned with the detailed 

 examination of the transformation of the radioactive bodies in 

 their connexion with the new generalization. Dr. Soddy is a very 

 clear expositor ; in only one or two cases are we left in a state of 

 doubt as to how far the statements made are conjectures, and how 

 far they represent experimental facts. 



We call special attention to the helicoid representation of the 

 periodic law on p. 11. 



XXI. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxvii. p. 1037.] 



February 25th, 1011.— Dr. A. Smith Woodward, F.R.S., President, 

 in the Chair. 



r PHE following communications were read : — 



1. 'Acid and Intermediate Intrusions and Associated Ash- 

 Necks in the Neighbourhood of Melrose (Roxburghshire).' 

 By Rachel Workman McRobert, B.Sc. 



This communication deals with the igneous rocks which fall 

 within an area about 7 miles square, included in Sheet 25 

 of the Geological Survey map of Scotland, and which lie in the 

 neighbourhood of Galashiels, Selkirk, and Melrose. The age usually 

 assigned to the igneous intrusions is a late period in the history of 

 the 'plateau-eruptions' of Calciferous Sandstone times, and thus 

 corresponds to those of the trachvtic lavas and intrusions of the 

 Campsie and Renfrewshire Hills. 



The relation of the igneous rocks to the Old Red Sandstone is 

 discussed, and new localities are cited where a protective covering of 

 igneous rocks has resulted in the preservation of small outliers of 

 Old Red Sandstone, far removed from the main outcrop of the 

 formation. 



