ANNIVEESAKY ADDRESS OF THE PRESIDENT. 59 



attractions, and for a time palaeontology was of less account than 

 mineralogy, the fossil contents of the earth's crust attracted less 

 attention than its mineral structure. But some forty years ago the 

 majority of geologists yielded to the fascination of the vast field which 

 a study of fossils opened out before them : and exact petrology, at any 

 rate in England, found few followers after the death of De la Beche. 

 I do not say this as a reproach — it is well that each generation 

 should do the work which lies ready to its hand ; and I can under- 

 stand that the great mystery of life will always induce (and, I may 

 say, rightly induce) the majority of thoughtful men to incline to a 

 study of the organic rather than of the inorganic world. Further, 

 the older generation of petrologists had gone about as far as was 

 possible with the means at their disposal ; the revival of petrology 

 has been due to the application of the microscope to the investi- 

 gation of its problems. In this respect we may feel a just pride in 

 remembering that to one of our countrymen, Dr. H. Clifton Sorby, 

 a former occupant of this chair, belongs the honour of being among 

 the very first to appreciate the importance of this mode of investi- 

 gation and to place himself at its head. 



At the present time the study of petrology is encompassed with 

 not a few difficulties, some inherent, some temporary. It may be 

 useful, even at the risk of giving offence, if I glance briefly at these. 

 To begin, the study is not, and can hardly ever be, a popular one. 

 To be an ideal petrologist it is necessary to be a good chemist, 

 physicist, mineralogist, and field-geologist ; and who can hope to 

 combine qualifications so diverse ? Again and again I have found 

 myself sharply stopped by my ignorance of chemistry, of physics, or 

 of mineralogy, or by want of leisure to undertake along journey for 

 the purpose of study in the field. These difficulties, however, will 

 always more or less exist, and we must be content to do our best 

 with the means at our disposal. But there are also difficulties of a 

 more temporary nature. One is that geologists, as a body, under- 

 value rather than overvalue the difficulties of the subject, and seem 

 disposed to treat it as a playground whereon they may relax from 

 severer studies. As regards this, I venture to assert that, at the 

 present stage of our knowledge, crude fancies and vague hypotheses, 

 founded on a few imperfectly observed facts, can do nothing but 

 cumber the ground and impede the progress of students. Xo ob- 

 servation on any point of real difficulty is of the slightest value 

 unless it be substantiated by careful study with the microscope. 



Closely akin to this is another difficulty, that the evidence cannot 

 be presented ad populum. "What is seen with the microscope 

 depends not only upon the instrument and the rock-section, but 

 also upon the brain behind the eye of the observer. Each of us 

 looks at a section with the accumulated experience of his past 

 study. Hence the veteran cannot make the novice see with his 

 eyes ; so that what carries conviction to the one may make no appeal 

 to the other. This fact does not always seem to be sufficiently 

 recognized by geologists at large. In similar palaeontological ques- 

 tions, such as the structure of plants or of protozoans, I have 



