NATURE 



[May 6, 1875 



person from another country is likely to be. It seems to me, 

 however, that the diminution in the number of geologists, com- 

 pared with the students of other sciences, if not in absolute 

 number, is clear on simple inspection of the field. It is true 

 not only of Great Britain, but of France and America as well. 

 Of mining engineers there is, I believe, a great plenty ; but of 

 men who are trained in field work, who can be trusted to unravel 

 a set of rocks, or who care for the science as a science, and not 

 as a means of winning a living, there are far too few. 



A year ago I had to organise a geological survey in the State 

 of Kentucky. I needed three topographers and three assistant 

 geologists who could stand alone. I picked my topographers 

 from over a hundred competent applicants ; 1 should have 

 searched in vain for months for two of my geologists, had it not 

 been that the suspension of the Missouri Survey gave me trained 

 men. But for this I should have been driven to Germany, that 

 inexhaustible reservoir of trained men, for my helpers. In 

 our schools it is still worse : geology is taught in the air, not on 

 the earth. The student never gets into the field for practical 

 work, and the science remains for him a thing of names and 

 shadows. With the hope of doing something to remedy these 

 evils, there is to be a Summer School of Geology, intended for 

 teachers of geology and those who propose to make special 

 workers in the science, taught in connection with the work of 

 the Kentucky Geological Survey ; it will be, in fact, though 

 taught in Kentucky (or the present, the Harvaid Summer Term 

 in Geology, all the instructors in that department from this Uni- 

 versity taking a part in its work. Eight or more of the assistants 

 of the Kentucky Survey will also be emplojed as instructors. 

 Already over one hundred persons have applied for admission to 

 the school, but the number will be limited to thirty : this list 

 now includes twenty-five teachers of schools of academic grade, 

 and five graduates of colleges who propose to become geologists. 

 As the school will be placed in a camp, it will be possible, if it 

 succeeds, to establish it in a new region each year, so that 

 teachers attending for, say, three years in succession, may get 

 a fair notion of our rocks, and, whai is better, learn how to 

 do field work. I believe that the novelty of the life, the 

 freedom and fresh air, will make it posiible lor teachers to use 

 their vacation time in study without damage. I am not without 

 hope that in this way teachers may be trained to their work, and 

 beginners provided with that practical introduction to geology 

 which it is now so hard to obtain. N. S. Shaler 



Harvard University, April i8 



[We append the programme of the Summer School of Geology 

 referred to by Prof. Shaler, in the hope that something similar 

 may be inaugurated here.] 



Harvard University. 

 Summer Instruction in Geology, 1875 



In order to furnish an opportunity for teachers in natural 

 science and special students in Geology to become acquainted 

 with the methods of practical work in that science, a Summer 

 School of Geology will be established, .during the months of July 

 and August, at a camp near Cumberland Gap, in the State of 

 Kentucky. This place has been chosen on account of the 

 eminent advantages it offers for the study of a great section of 

 the American Pahcozoic rocks, and of the structure of the Appa- 

 lachian Mountains, and on account of the co-operation of the 

 Kentucky Geological Survey which is promised in a letter from 

 the Governor of that State to the I'resident of the University. 

 It is also a very healthy region. 



The special object of this school will be to teach students to 

 observe, but instruction will be provided in Physical Geology, 

 Historical Geology and Palaeontology, Chemical Geology, and 

 Topographical Engineering, as far as these subjects are connected 

 with geological work . The instruction will be necessarily in- 

 complete, and will be expressly diiected to the elucidation of the 

 problems furnished by the area to be explored. The co-opera- 

 tion of six well-qualified instructors has already been secured, 

 and a number of other able geologists have promised their pre- 

 sence and their aid in teaching. Some instruction in the zoology 

 and botany of the neighbouring region will probably be given to 

 those who desire to receive it. Certificates of attendance will 

 be given at the end of the time. The number of students will 

 be limited to thirty, and men only will be accepted. No pre- 

 vious knowledge of the science is required, but only graduates of 

 colleges, teachers, or other persons who can give evidence of 

 maturity and some training can be admitted. 



Persons wishing to join the school should at once address 



J. VV. Harris, Secretary of Harvard College, Cambridge, Mass. 

 Before their enrolment they will be required to pay the fee of 

 fifty dollars for tuition, use of tents and camp equipage, and 

 transportation about camp. In case anyone is prevented from 

 joining the school by illness this fee will be remitted, provided 

 the notice thereof is given before June 15. They will also be 

 required to pay weekly in advance the estimate for subsistence 

 and camp servants (which is not expected to exceed three dollars 

 per person). 



Persons joining the school from the west will report themselves 

 on June 24 and June 30, at the terminal station on the Lebanon 

 Branch of the Louisville and Nashville Railroad. Those joining 

 from the east will be met at a station hereafter to be designated 

 on the East Tennessee Railroad, on June 26 or July I. Persons 

 unable to join on these days should notify the chief of camp, 

 Mr. John R. Proctor, Lexington, Ky., who will arrange for ihtir 

 transportation to camp. 



All students are expected to provide themselves with the fol- 

 lowing articles : — Two blankets, a pocket magnifying-glass, a 

 pocket compass ; Dana's " Manual of Geology," revised edition 

 (1874), and Lyell's "Principles of Geology." Suitable note- 

 books will be provided at cost. Students should also provide 

 themselves with two suits of old clothes, flannel shirts, and stout 

 boots. The total amount of baggage should not exceed seventy- 

 five pounds for each person. An effort will be made to secure a 

 reduction of fares on the railroads leading to the camp. 



The Attraction and Repulsion caused by the Radiation 

 of Heat 



Will you allow me to say a few words in reference to the 

 report of Mr. Crookes's paper which appeared in Nature, vol. 

 xi. p. 494. Apparently 2\Ir. Crookes does not understand the 

 nature of the forces which I have shown to result from the com- 

 munication of heat between a gas and a surface ; otherwise he 

 would not bring forward as conclusive against the supposition 

 that the phenomena which he has discovered are due to these 

 forces, experiments which show entirely the other way. As I 

 have previously explained, it follows as a direct result of the 

 kinetic theory of gas, that if such forces as I have supposed exist 

 for a certain tension of the gas surrounding the suriace, they will 

 not be diminished by diminishing the tension of the gas ; and 

 consequently no amount of pumping would destroy such forces 

 where they once existed. Whereas the smaller the tension of 

 the gas the freer the surface will be to move, and the less its 

 motion would be opposed by convection currents ; hence, on the 

 supposition that the motion is due to these forces, the only effect 

 of improving the vacuum would be to intensify the action. An l 

 this being the case, it is clear that Mr. Crookes's experiments, in 

 which he finds that the action still remains in the most perfect 

 vacuum which he has obtained, tend to support and not to upset 

 my conclusion that the actions are due to these forces. The fact 

 that Mr. Crookes finds it impossible to conceive this only shows, 

 as I have said, that he does not comprehend the nature of the 

 forces ; for it certainly presents no greater difficulty than the fact 

 that the velocity of sound is independent of the tension of the 

 gas through which it is transmitted. 



Mr. Crookes still appears to think that I attribute these forces 

 solely to the presence of condensable vapour. It is true that the 

 title of my first paper might have led him into this error had be 

 read no further ; but both in that paper and in a letter to the 

 Philosophical Magazi7ze {qx November 1874 it is clearly sbowa 

 that this is not the case. 



I am in hopes that ere long we may hear something on this' 

 .subject from Prof. Maxwell, who probably knows more about 

 the kinetic theory of gases than anyone else. If I am right, these 

 experiments afford a direct proof of the truth of this theory ; and' 

 as far as I know, this is the only direct proof that has ever been 

 obtained. I do not mean to say that this is the most conclusive- 

 proof, but the most direct, or, to quote a remark of Dr. Balfour' 

 Stewart, " These experiments stand in much the same relation, 

 to the kinetic theory of gases that Foucault's pendulum occupied 

 with regard to the rotation of the earth." No one can admire- 

 more than I do the experimental skill with which Mr. Crookes 

 has brought the phenomena to light ; nor can I see, should it 

 turn out as I maintain, that they have led to the discovery of ai 

 law of nature, that this will detract from their importance, eveni 

 if they lose somewhat in general interest from the breaking up- 

 of the halo of mystery with which they have hitherto been sur-» 

 roimded. Osborne Reynolds 



Owens College, Manchester 



