70 Scientific Intelligence. 



their wave-lengths when the medium surrounding the conductor 

 changes. — Ann. der Physik., No. 11, 1890, p. 435. J. T. 



13. Seat of the Moon and the Stars. — C. V. Boys has used his 

 radio-micrometer to detect the heat of the stars and the moon. 

 Although the instrument was competent to detect the heat of a 

 candle at a distance of 2*8 kilometers, an image of the brightest 

 star produced by a silvered concave mirror of 16 inches aperture 

 produced no sensible indication. The moon, however, gave large 

 indications, and the author discusses the radiation from the moon 

 by the method of curves. The radio-micrometer could detect 

 TToVoj °f tDe entire heat radiation from the moon. — Proc. Roy. 

 Soc. Lond., 47, p. 480-499, 1890. j. t. 



14. Foam. — Lord Rayleigh in his investigation upon surface 

 forces discusses the question of the formation of foam and con- 

 cludes that a certain amount of impurity and want of cleanliness 

 is necessary for the formation of foam. Foam cannot be formed 

 in chemically clean substances. Calculation shows that the thick- 

 ness of oil which is necessary to stop the movement of small 

 pieces of camphor over a definite surface area of water amounts 

 to only 1*5 millionths of a millimeter. — Proc. Roy. Soc, 28, 

 March, 1890. j. t. 



15. A photochronograph. — M. Makey attaches to one end of 

 a long band or ribbon of sensitive film a band of black opaque 

 paper and to the other end of this film a similar band of red 

 paper. The film is then rolled upon a bobbin beginning with the 

 end of the red band. This operation is conducted in the dark 

 room. The bobbin can afterwards be taken into the light, being 

 fully protected by the black and red bands of paper. When one 

 wishes to take a number of photographs of a rapidly moving ob- 

 ject, the bobbin is introduced into the photographic apparatus. 

 One end of the band rolls upon an empty bobbin and at the end 

 of the operation the film is protected by the band of red paper. 

 While the portion that is not exposed to the light is still covered 

 with the black band, one can thus readily distinguish between 

 the portions of the bobbin that have been exposed to light. The 

 apparatus makes it possible to take a number of images upon the 

 same band and consequently to submit tbem all at once to the 

 same developer. — Connotes Rendus, Nov. 2, 1890, p. 626. j. t. 



16. Photographic Sensitives. — H. W. Vogel discusses the ques- 

 tion of the different sensitiveness of plate sensitized with eosine 

 and erythrosine according to different methods. A solution of 

 erythrosine in water shows an absorption band near E. A more 

 concentrated solution gives a band lading into the blue. The 

 addition of silver causes these bands to disappear and in their 

 place appears between E and D a weaker band. These absorp- 

 tion bands are so decided that they afford a very sensitive means 

 of deciding whether one is employing an eosine or a eosine silver 

 plate. — Beiblatter Ann. der Physik, No. 10, 1890, p. 983. j. t. 



