Notes and Memoranda. 479 



The Reflection op Light employed to indicate Changes op 

 Temperature. — Dr. Boulon, of Paris, uses the reflection of light 

 very ingeniously, for the purpose of making very slight changes of 

 temperature distinctly visible, by their effects, to a large audience. 

 He employs •& thermo-electric battery, which is so arranged that 

 the electric current produced by changes of temperature is trans- 

 mitted through the helix of a galvanometer, the needle of which 

 has, fixed upon its centre, a very small mirror. Opposite to this 

 mirror is a large screen, in the middle of which is a small aperture, 

 through which a ray of light from a bright lamp behind it passes to 

 the small mirror in front of it. When the plane of the mirror is 

 exactly perpendicular to the direction of the ray from the aperture 

 in the screen — that is, when there is no electric current to deflect the 

 needle of the galvanometer — the ray is reflected back again through 

 the aperture. But the smallest current deflects the needle, and 

 therefore turns the mirror round in one direction or the other ; 

 and the ray, instead of passing back through the aperture, is thrown 

 on the screen to the right or left of it. The most minute changes 

 of temperature are thus rendered distinctly and easily, cogni- 

 zable by any number of persons, in a large lecture-room. 



NOTES AND MEMORANDA. 



Musical Frogs. — The author of that excellent book, Ten Years in 

 Sweden, speaks of the Bombinator igneus, a little frog that has become naturalized 

 in that country, as emitting, during tbe pairing season, a note like the ringing of 

 bells. He says, " As this sound proceeds from the depth of the water, it appears 

 to come from a long distance, although the frog may be within a few fathoms." 

 Linnaeus spoke of the same reptiles making sounds as if large bells were ringing 

 in the distance. It would be very interesting to naturalize the little creature in 

 this country. 



New Planet. — M. de Gasparis has discovered another new planetoid on the 

 26th of April, which, in honour of Dante, has been named Beatrix. 



The Obliquity of the Flounder. — Professor Steanstrup has obtained 

 specimens which show that in its early stages the flounder is a symmetrical fish, 

 ■with one eye on each side of its body. As it grows, both eyes pass to one side, in 

 which they have a curious oblique arrangement. He says, " The symmetrical fish 

 by degrees squints its eye in and up through the head out to the other side, and 

 at last squints itself into a perfect flounder." Professor Wyville Thompson, who 

 has recently examined Professor Steanstrup's collection of flounders in various 

 stages, confirms the main fact, but suggests in the Annals of Natural History a 

 more probable mode of effecting the change than the passage of the eye through 

 the vault of the cranium, as conceived by Steanstrup, with whom he agrees in 

 rejecting Van Beneden's hypothesis, that it is produced by a simple torsion of the 

 anterior portion of the head. From various considerations, he thinks that " the 

 eye of the blind side passes to the eye-side, not through the vault of the head, 

 but under its integument, displacing in its progress the frontal bone on its own 

 Bide. . . . The term ' migration' of the eye is of course used in a somewhat 

 metaphorical sense. The eye changes little in actual position. With the growth 

 of the fish the associated parts are, as it were, developed past it, producing this 

 singular obliquity." 



