Colour of Substances and their Magnetic Properties. 217 



of a moth, was repelled, evidently by a quantity of dried gelatinous 

 matter with which it was filled. 



The leaves and corollas of plants proved to be better adapted for 

 the inquiry ; still, for definite results, not nearly so much to be relied 

 on as the chemical compounds I have already given. The lignine, 

 or matter forming the walls of the sac, which is now known to be 

 the skeleton of every vegetable production, is nearly inert before the 

 magnet, but when charged with water or resin, then the tendency is 

 to leave it ; and this frequently occurs in flowers and organic bodies 

 irrespective of their colour. For example, sap green, a precipitate 

 by lime from a red-coloured vegetable juice, has a very dark green, 

 nearly black colour, and a slight diamagnetic tendency. By alcohol 

 a translucent yellow-green substance is dissolved out, which is dia- 

 magnetic, while the residue, a dark earthy- green body, is attracted 

 by the magnet. From a number of experiments with coloured parts 

 of plants of various shades, I find the white and pale yellow repelled, 

 while the darker and less tranlucent colours are attracted by the 

 magnet. Among the repelled are the corollas of the white daisy and 

 pale yellow everlasting flower; calyx of the snowdrop when fresh, 

 but attracted when it begins to wither ; rein-deer moss, and some 

 light-coloured green leaves in a moist state. Among the attracted 

 are the oak and fern leaves dried brown, tutsan leaves dried, black tea, 

 rose corolla leaves, only after the odoriferous matter was well washed 

 out, dark green leaves of evergreens, either fresh or dried, corolla of 

 the common gorse, wallflower, deep-coloured violets, primroses of a 

 reddish-brown hue, polyanthus corolla dark-coloured, and some lilac 

 and crimson leaves of flowers. 



With the approach of summer I look forward to being able to 

 increase the number of diamagnetic corollas, which probably may be 

 got of every hue provided they have sufficient translucency, a condi- 

 tion the foregoing inquiry has shewn to have so much influence in 

 producing the property of magnetic repulsion. 



On the Physiognomy of the Islands in the Pacific. By Mr 

 James D. Dana. 



The valleys of the Pacific Islands have usually a course from the 

 interior of the island towards the shores ; or when the island con- 

 sists of two or more distinct summits or heights (like Mani), they 

 extend nearly radiately from the centre of each division of the island. 

 They are of three kinds : — 



I. A narrow gorge, with barely a pathway for a streamlet at 

 bottom, the enclosing sides diverging upwards at an angle of thirty 

 to sixty degrees. Such valleys have a rapid descent, and are bounded 

 by declivities from one hundred to two thousand feet or more in eleva- 

 tion, which are covered with vegetation, though striped nearly horizon- 



