SCIENTIFIC NEWS. ^ll 



latitudes of the five principal stations. The third and last 

 volume is in the press. 



Mr. Berthoud, who died in August 1807, had published Treatise on 

 a few days before his death a supplement to his treatise on ime ee i )ers> 

 Timekeepers, with an account of his researches from 1752 

 to 1807. 



Mr. Betancourt presented to the class a model of a lock Lock for 

 on the same principle as that invented by Mr. Huddleston. camUl * 

 [See Journal, Vol. IV, p. 236.] He has likewise given a 

 mathematical discussion of the principles, on which it ought 

 to be constructed, so as to be manageable by the strength 

 of one man. 



* Mr. Lancret has considerably extended Mr. Monge's Evolute*. 

 theory of evolutes. 



Mr. Mains, of the corps of engineers, has deduced from a Propagation of 

 uniform and general analysis the various circumstances of^S 111 * 

 the propagation of light, and a solution of the fundamental 

 problems of optics. By a theory entirely new, founded on 

 the properties of the intersections of a series of right lines, 

 drawn, according to a constant law, to all the .points of a 

 ^iven surface, Mr. Malus has determined the course of re- 

 fracted and reflected rays; the intensity of light, in all 

 cases, at any given distance from the luminous point ; and 

 the place, form, and magnitude of images. He shows, 

 that in certain, cases,, and with certain surfaces, reflection 

 and refraction produce images, that are erect in one of their 

 dimensions, and inverted in the other, a circumstance never 

 before noticed*. 



The propagation and reflection of sound have some re- Propagation 



* The plane mirror, or common looking-glass, in fact shows objects 

 erect in the perpendicular, and inverted wilh respect to right and left. 

 But this is not what the reporter means, though he does not inform us, 

 what the construction of the mirror of Mr. Malus is. It would be found 

 however, that a mirror, which is a section of a concave cylinder, will l *u- °i 

 represent the horizontal dimension of an object the reverse of what a 

 plane mirror v>ould do, without affecting the perpendicular ; in other 

 words, the spectator would see the image of himself, or anv other object 

 in it, exactly in the same position, as if he stood facing the object, that 

 occasioned the image : and this no doubt is the mirror alluded to, which 

 is of a kind, that 1 do not recoliect to have seen mentioned. C. 



semblance 



