102 Prof. T. R. Lyle on the Variations of 



of the theory is probably a distinct advantage to it when com- 

 pared with other theories of climatic change ; but still the 

 theory need not be regarded as antagonistic to other theories, 

 especially to those which have reference to changes in local 

 conditions. There can be no doubt that variable local con- 

 ditions, such as the height of the land above sea-level, the 

 distance from the sea, and the direction of prevailing winds 

 and ocean currents, have a very great influence on the climate 

 of any particular locality. However, it is fairly well re- 

 cognized that variations in local conditions like the above 

 cannot be regarded as at all sufficient to account for the facts 

 observed in connexion with the climatic changes of geological 

 history, and a more generally operating cause must be sought 

 for, such as we have in the variability of the carbonic acid 

 of the atmosphere. Though I do not venture to make any 

 definite statement about any observed connexion between 

 volcanic activity and geological climate, I hope that geo- 

 logists will state their views on the subject ; and if it should 

 be considered that there is not enough evidence to draw 

 a definite conclusion, I hope that by and bye a sufficient 

 amount of evidence will be obtained. In any" case, as already 

 remarked, the large amount of coal deposited in the earth is 

 a strong argument in favour of the variability of the amount 

 of atmospheric carbonic acid ; and as it is usually considered 

 that the periods in which large quantities of coal were 

 deposited were warm periods, it is obvious that this also 

 to some extent supports the view that there is a connexion 

 between the amount of atmospheric carbonic acid and the 

 general temperature of the atmosphere and surface of the 

 earth. 



VIII. Investigation of the Variations of Magnetic Hysteresis 

 with Frequency. By Thomas R. Lyle, M.A., Professor 

 of Natural Philosophy in the University of Melbourne *. 



[Plate II.] 



IN the following paper are given some results obtained by 

 my wave-tracer, of which a description has been published 

 in the ' Philosophical Magazine ' for November 1903. 



The work described, which is of a preliminary nature, 

 was in great part performed more than a year ago, but a 

 severe illness has prevented me until now both from preparing 

 it for publication and from continuing as intended the same 



* Communicated by the Physical Society : read November 11, J 904. 



