254 Chronicles of Science. [April, 



to determine the solar parallax from the transit of Terras in 1874. 

 It is illustrated by fifteen pictures of the earth on her passage 

 through the shadow-cone of Venus. The object of the paper is to 

 show how photographs of the sun may be so taken, at different 

 stations, that the relative displacement of Tenus may be on a radius 

 of the sun's disc. 



In another paper he exhibits a method of constructing charts by 

 which the great circle course between any two points on the globe 

 may be accurately and quickly obtained. 



Mr. Browning has invented a new fomi of micrometer for mea- 

 suring the position of lines in faint spectra. By this arrangement 

 an image of a bright cross is thrown on the spectrum, which it can 

 be made to traverse by turning a micrometer screw. The ad- 

 vantages of the plan will be appreciated by those who know the 

 difficulty of determining the position of the spectral lines by the 

 usual arrangement. 



4. BOTANY. 



Influence of Climate and Soil upon Plants. — M. Kemer, of Inns- 

 bruck, has published a very interesting pamphlet on this subject, 

 one of great importance in relation to the question of the origin of 

 species. In the centre of distribution of a species, where it reaches 

 its maximum of abundance, it is very unusual tor varieties to become 

 established; since, even if deviating forms were to appear, they 

 would not be perpetuated, in consequence of the law of nature that 

 cross-fertilization with other individuals, rather than seh-fertilization, 

 is the rule. On the outskirts, however, of the region of distribu- 

 tion, where the individuals are very scattered, a variation once 

 appearing is likely to become established ; because, the chances of 

 self-fertilization being much greater, the peculiarities are likely to 

 be perpetuated by heredity. Here therefore we must look for 

 those aberrant forms which become the ancestors of new species. 

 The author believes the direct influence of climate or soil in origi- 

 nating changes in the structure of plants to be extremely small ; 

 these changes being effected only in the course of many generations 

 by the process of natural selection, those individuals which exhibit 

 slight divergences suitable to the circumstances in which the plant 

 is placed being most likely to survive, and to produce large numbers 

 of seeds. Changed conditions of life can kill a plant, or destroy its 

 health, but can have no direct influence in transforming it into a 

 form more suitable for those conditions. Asa contribution towards 

 a series of observations on the relation between the flora of a coun- 

 try and its natural conditions of soil and climate, M. Kemer has 

 paid special attention to the general features of the flora of the 



