MACHINES DRIVEN BY SOLAR RAYS. 337 



rationally. If lie had lived now, a corresponding education would cer- 

 tainly have put him in possession of the very simple facts which I have 

 placed hefore you ; and the application to them of his own methods 

 of reasoning would have taken him as far as we have been able to go. 

 But, thirty years ago, Herodotus could not have obtained as much 

 knowledge of physical science as he picked up at Halicarnassus in any 

 English public school. 



Long before I had anything to do with the affairs of Eton, how- 

 ever, the Governing Body had provided the means of giving such in- 

 struction in physical science as it is needful for every decently-educated 

 Englishman to possess. I hear that my name is sometimes peculiarly 

 connected (in the genitive case) with certain new laboratories ; and, if 

 it is to go down to posterity at all, I would as soon it went in that 

 association as any other, whether I have any claim to the left-handed 

 compliment or not. But you must recollect that nothing which has 

 been done, or is likely to be done, by the Governing Body, is the doing 

 of this or that individual member ; or has any other end than the deep- 

 ening and widening of the scheme of Eton education, until, without 

 parting with anything ancient that is of perennial value, it adds all 

 that modern training which is indispensable to a comprehension of the 

 conditions of modern life. 3Iacmillan , s Magazine. 



MACHINES DRIVEN BY SOLAR RAYS. 



By GASTON TISSANDIER. 



OUR readers have already been informed* respecting the solar 

 machines constructed by MM. Mouchot and Abel Pifre, in which 

 the heat of the sun is employed, either directly or through the agency 

 of steam generated directly by it, as the source of power, and of their 

 successful application to certain purposes in Algeria. M. Pifre, who is 

 an assistant to M. Mouchot in his engineering work in Algeria, has con- 

 tinued his experiments, and made some improvements in the machines, 

 by which their operation has been rendered more effective. The princi- 

 pal improvement is in the form of the reflector, or insolator, by means 

 of which the rays of the sun are concentrated upon the boiler or other 

 object to be heated. M. Mouchot's reflector was in the form of a 

 simple hollow cone, formed with a straight line of projection. M. 

 Pifre bends the line of projection so as to give it three different in- 

 clinations, and thereby obtains for the surface of his mirror a form 

 nearly like that of a paraboloid. An interesting experiment upon the 

 possibility of adapting the apparatus of M. Pifre to a European sun 



* " Popular Science Monthly," vol. xviii, p. 283, and vol. xviii, p. 432. 

 VOL. xxin. 22 



