386 Chronicles of Science. [July? 



Mr. Cleveland Abbe presents a paper on the distribution of 

 Nebulae. He finds evidence that clusters and planetary nebulae 

 belong to the Yia Lactea, while other nebulae form independent 

 systems, of which the Nubeculae are members. It does not appear 

 to have occurred to those who have dealt with this subject, that the 

 marked absence of nebulae from the zone of the Via Lactea affords 

 as striking evidence of a close relation between the nebular and 

 sidereal systems, as the contrary phenomenon of aggregation along 

 that zone would have afforded. 



Mr. Kincaid describes an instrument called a metrochrome, for 

 detecting changes of star-colours. Such changes have only been 

 certainly noted, as yet, in the case of Sirius and 95 Herculis. 

 They are very difficult to detect, since observers differ greatly in 

 their estimate of colour. Spectrum analysis requires " superlatively 

 fine" weather, and is also for other reasons surrounded by great 

 and numerous difficulties, which render its application almost im- 

 practicable. The great difficulty, so far as other methods are 

 concerned, lies in the selection of a standard of reference. A 

 painted scale, like that given by Admiral Smyth, is objectionable 

 on account of the opacity of its colour ; and is further not suffi- 

 ciently reproducible. Precious stones are beyond the reach of most 

 observers. It has been suggested by Mr. Proctor that the illumi- 

 nation of a minute white disc in the focus of a positive eye-piece, 

 " through differently coloured glasses placed on a rotating disc," is 

 a- method which might be employed with advantage. Mr. Kincaid 

 prefers the use of chemical solutions (a method suggested by Mr. 

 Huggins). He uses a rotating drum with six equidistant openings, 

 three of which are so constructed as to admit flat-sided stoppered 

 bottles containing differently coloured chemical solutions ; the other 

 three openings transmit the normal light of the lantern. By wholly 

 or partially covering one or more of the former openings, and by 

 communicating a rapid rotation to the drum, it will be possible to 

 reproduce the light of a particular star. This light thrown into 

 the telescope produces the image of an artificial star. 



4. BOTANY, VEGETABLE MOBPHOLOGY, AND 

 PHYSIOLGY. 



America. — Origin of the Canadian Flora. — Dr. Dawson, of 

 Montreal, has published in the ' Canadian Naturalist ' a list of some 

 species of plants he has found in the well-known deposit of Leda- 

 clay at Green's Creek, on the Ottaway, from which he has been 

 able to arrive at a satisfactory estimate of the climate prevailing- 

 there at the time of their deposit. Among the species are, Drosera 



