Prof. J. F. Blake— Reply to Criticisms. 169 



Spaces? This, however, I have not ventured to discuss, but only to 

 criticize the actual arguments brought forward in this connexion. 

 I wrote "sic" after the word atoms partly because it sounded so 

 funny to read of the " atoms and molecules of which minerals are 

 composed," which is like saying that a sentence is composed of 

 letters and words, and partly because I was not sure whether the 

 phrase was a mere redundancy, or whether it was actually intended 

 to be stated that heat enlarged the distance between the atoms in 

 a molecule. This may be the case for all I know, but I do not 

 think it can be quoted as a generally admitted fact. General 

 MacMahon will thus see that his somewhat cruel inference as to 

 wh}'^ I wrote " sic " is not corrrct. 



My illustration about hydrate of sodium sulphate is more to the 

 point than Gen. MacMahon appears to think — the gist of it is that 

 it gives an example of dehydration bj^ heat in the presence and not 

 " in the absence of water." General MacMahon says he was con- 

 sidering capillarjr flow under heat and pressure, but in the paper he 

 really only discusses the action of heat, and the present discussion 

 on the effect of pressure is a new one. In reply to it, however, 

 it may be said, that though, under the circumstances, inci'ease of 

 pressure may be accompanied by increase of head of water, the 

 effect of pressure on the mineral or rock would be to close the pores 

 and retard the supposed capillary action, just as a squeezed sponge 

 will not hold so much water as a loose one. On the other hand, it 

 would facilitate a certain kind of chemical change by bringing the 

 molecules more within range, and might thus cause hydration, not 

 mechanically, but chemically ; other kinds of chemical change it 

 would retard. 



2. Mr. S. S. Buckman complains that statements which are really 

 his are made to appear as mine. I cannot find them. Everything 

 not in squai'e brackets is supposed to originate with the author of 

 the paper. He cannot see that his species are of a " most restricted 

 kind " because he has only made five new species out of 27. True ; 

 but the other 22 are already of the most restricted kind. I have 

 not a word to say against, but only admiration for. the principle of 

 working out genetic series ; but a genetic series is not a zoological 

 genus, but something more restricted ; and the reasons relied upon 

 by Mr. Buckman, when given, for considering two forms genetically 

 connected are certainly to me in many cases " apparently arbitrarj'." 

 Take the case discussed of Haugia occidentalis. It is said to be a 

 senile form, and to have lost the knobs characteristic of the variahilis 

 group. But the only proof offered that it belongs to the group is 

 the statement (under H. Eseri) that this " is very plain from their 

 suture line " which is nowhere either figured or described for 

 H. occidentalis that I can find ; and though the author subdivides 

 the strata most minutely, this and the knobbed forms occur in the 

 same subdivision. Is not then the assumption that this is a senile 

 form of a knobbed genetic series an arbitrary one ? 



Next as to H. Esei-i. Is it possible, indeed probable, that the 

 figures 3, 4, are meant for the true E. Eseri of Oppel ; but fig. 3 is 



