344 T. Mellard Reach— Secular Straining of the Earth. 



Victoria, under the provisional title of Didymograptus JPantonii, 

 McCoy. 1 



McCoy, however, in the same year, but apparently at a 

 later date, described the form in question as a species of Tetra- 

 graptns, Salter, and as probably identical with Tetragraptus fruticosus, 

 Hall. 2 This view of the affinities of Didymograptus Pantonii, McCoy, 

 was later accepted by Mr. Etheridge. 3 At the same time it is possible, 

 that one of the two forms placed by Mr. Etheridge, in his original 

 paper in the "Annals" (Joe. cit. pi. iii. fig. 21), is really a species of 

 Didymograptus, and perhaps may be identical with my Didymograptus 

 Y-fractus, Salter, var. voJucer. Owing, however, to the fact, that 

 the figure just alluded to only shows a part of the basal portion 

 of the polypary, it is not possible to make this assertion with any 

 confidence. 



The only other form which may be alluded to is that named by 

 Baily Didymograptus Bisingeri, from the Lower Bala rocks of Ireland, 

 which has been included by Herrmann in the group of Didymograptus 

 Y-fractus, Salter. 4 I am not aware, however, that this form has 

 been either described or figured, and I am therefore unable to offer 

 any opinion as to its real affinity. In conclusion, I wish to express 

 my great indebtedness to Professor Lapworth, F.K.S., for his most 

 friendly assistance and advice in the preparation of this notice. 



III. — Secular Straining of the Earth in Belation to the 



deep Phenomena of Volcanic Action. 



By T. Mellard Reade, C.E., F.G.S., etc. 



THE application by Dr. Johnston-Lavis of the theory of the 

 secular straining of the Earth, with which my name and Mr. 

 Davison's is connected, to an explanation of the deeper phenomena 

 of volcanic action, is ingenious and suggestive. 5 It will, therefore, I 

 trust, be of some use if I am allowed to discuss and criticize the 

 principles and propositions that appear to me to be necessarily 

 involved in the views put forth by Dr. Johnston-Lavis. Before 

 doing this, I feel it incumbent upon me to point out that Mr. 0. 

 Fisher's position with regard to the question seems to have been 

 misunderstood. So far from occupying an antagonistic position, 

 he has done much to mathematically develop the theory ; and it is 

 only when we come to its practical application to the explanation 

 of geological phenomena, that he, myself and Mr. Davison differ. 



In the "Origin of Mountain Banges," and elsewhere, I have 

 expressed the opinion that it is "a weak point in most theories of 

 volcanic action that the machine^ invoked is insufficient to bring up 

 molten matter from a great depth." I agree with Dr. Johnston- 

 Lavis that the continuous outflow of lava, which has taken place 

 since the dawn of geological history, demands a supply of heat drawn 



1 Ann. and Mag. Nat. Hist. 1874, vol. xiv. series iv. p. 7, pi. iii. figs. 21-22. 



2 Geol. Survey, Vict. 1874, dec. i. p. 13, pi. i. figs. 9-14. 



3 A Catalogue of Australian Fossils, by E. Etheridge, jun., F.G.S., 1878. 



4 Die Graptolithenfamilie Dichograptidse, Otto Herrmann, 1885. 



5 Geol. Mag. June, 1890. 



