CHAPTER OF VARIETIES 



163 



objections, and be not capable of explaining- the phenomena, even if its 

 postulates be admitted ; yet the author of the present paper does not 

 assail it with any arguments of this kind. He has, on the contrary, 

 attacked it in its stronghold, and has endeavoured to bring it to the test 

 of direct experiment. 



Sir Isaac Newton considers the green colour of plants (the most gene- 

 ral colour which nature presents to us) as a green of the third order of 

 periodical colours, and has also given us the exact composition of this 

 particular colour. 



In order to determine the composition of the green colour of plants, 

 the author dissolved their colouring matter in alcohol ; and having ana- 

 lysed it by a fine prism, he found it to have, in every case, the same 

 composition. The portions of the spectrum, however, which entered 

 into its compound tint were totally different from its theoretical com- 

 position, as assigned by Sir Isaac Newton ; and had no relation what- 

 ever to the colour of their plates. The green colouring matter exercised 

 an arbitrary specific action upon different parts of the spectrum, and its 

 green colour was owing to its having absorbed a certain number of rays, 

 which, when subtracted from the white light, left the colour under 

 consideration. 



In order to render this result more general, the author examined an 

 immense number of coloured solutions, obtained from plants and arti- 

 ficial salts, and a great variety of coloured solids, either formed by art, 

 or obtained in nature ; and in all these cases he found no indication 

 whatever of periodical colours. The colours were invariably produced 

 by the absorption of certain definite rays taken arbitrarily and unequally 

 from different parts of the spectrum ; and, excepting in the case of cer- 

 tain imperfectly transparent and opalescent fluids, there never was the 

 slightest trace of a reflected tint similar to that which might have been 

 expected, had the Newtonian theory been true. 



On the Gradual Elevation of Land in High Northern 

 Latitudes, by J. F. W. Johnston, Esq., F. R. S. Ed.* — In this 

 paper, the author showed by a number of phenomena observable within 

 the coasts of Sweden, chiefly around Stockholm, and on the shores of 

 the lake Macler and its arms, that the conclusion of the Swedish sur- 

 veyors in 1821, that a change of the relative level of the land and water 



* Read before the Royal Society of Edinburgh. 



