Fro/essor T. G. Boniiei/ — Scliisfs in Lepontine Alpa. 165 



molecular changes of such importance were taking place in the 

 matrix of the rock.' Er sieht hier eine Thatsache, an der er zweifelt, 

 weil sie ihm unerkliirich vorkommt!" Well, then, I will tell 

 Professor Heim why I was not quite satisfied. In the first place, 

 if it be a sign of bias to reason inductively from cai'eful and 

 numerous observations, and to rely on the conclusions thus obtained 

 so far as to view with some suspicion any new phenomenon which 

 distinctly contradicts them, I admit the charge, and that un- 

 blushingly, for I believe this to be the method of science. The 

 latter is said by a good authority to be organized common-sense. 

 If in every-day life a number of credible persons agreed in stating 

 that something had occurred — say a man had done an action which 

 they had witnessed — should we not be justified in cross-questioning 

 rather severely anyone who suddenly appeared to swear an alibi? 

 Now all my work, and it was considerable, undertaken with the 

 sole desire of discovering the truth — work which had obliged me to 

 discard almost everything I learnt when young — had led me to 

 conclusions different from what Professor Heim was asserting.' 

 Inasmuch, then, as his " Mechanismus," while greatly impressing 

 me in some respects, had created suspicions of his trustworthiness as 

 a guide in petrology, I submit that I was justified in thinking it 

 possible he might have made a mistake. The ' Thatsache ' was ia 

 reality little more than his assertion. 



But he will say that I was shown the specimens. Yes ; and if 

 Professor Heim had seriously worked at petrology he would know 

 that conclusions founded on hand-specimens are much less trust- 

 worthy than those arrived at by examination of rocks in the field 

 or under the microscope. Speaking for myself, I refuse, when the 

 matter is difficult, to express an opinion on a hand-specimen, but 

 require to have a slice prepared for the microscope. Moreover, it 

 appeared to me, when looking at his specimens, that the matrix of 

 the two sets, those with belemnites and those with real garnets, 

 was somewhat different. Professor Heim would no doubt set down 

 this to ' bias,' but it is really the almost unconscious eft'ect of that 

 experience which most perso'ns acquire by long work at a particular 

 subject. It is very similar to the power which enables a specialist 

 to make a diagnosis of something which a physician, who has worked 

 along other lines, would not perceive. 



But he quotes another phrase to convict me of bias. "It was 

 very difficult to understand how such a fossil as a belemnite could 

 have retained its characteristic form while molecular changes ot such 

 importance were taking place in the matrix of tlio rock. 11ns 

 remark is evidently not intelligible to Professor Heim, so i will 

 endeavour to enlighten him. The results of contact-metamorphism, 

 to which I have paid considerable attention, most nearly resemble 

 the crystalline schists. In them, so far as my experience goes, 



' I may add that the general tendenz to minimize the effect of ' 'ly>';|"';;-™'«^2n 

 morphisni, 

 important 

 After ten 

 which 



