Notices and Analyses. 199 



as the surface It is also as the surface multiplied by the square root 



of the free action When the surface is constant, it is therefore as 



the square root of the attractive force. 



3. The interval which the accumulation can pass, is directly propor- 

 tional to the quantity of matter, and inversely proportional to the 

 surface. — It is as the quantity divided by the surface. — If the matter 

 and surface be either increased or decreased in the same proportion, 



the interval remains the same If, as the matter be increased, the 



surface be decreased, the interval will be as the square of the quantity 

 of matter. 



4. The force of electrical attraction varies in the inverse ratio of the 

 square of the distance between the points of contact of the opposed 

 conductors, supposing the surfaces to be plane and parallel ; or other- 

 wise between two points, which fall within the respective hemis- 

 pheres, at a distance equal to one-fifth of the radius, supposing the 

 opposed surfaces to be spherical. 



5. The free action is in a direct proportion to the square of the 

 quantity of matter, and in an inverse proportion to the square of the 



surface It is directly as the effect of the explosion on a metallic 



wire, all other things remaining the same If the matter and the 



surface increase or decrease together, and in the same proportion, the 

 attractive force remains the same. — If, as the matter be increased, 

 the surface be decreased, the attractive force is as the fourth power 

 of the quantity of matter. 



6. The effect of an electrical explosion, on a metallic wire, depends 

 exclusively on the quantity of matter, and is not influenced by the 



intensity or free action It is diminished by accumulating the matter 



on a divided surface. — It is as the square of the quantity of the 

 matter. It is as the square of the interval which the accumulation 



can pass It is directly as the attractive force of the free action, all 



other things remaining, in each case, the same It is as the momentum 



with which the explosion pervades the metal. 



't\ 



An Experimental Inquiry into the Number and Properties of 

 the Primary Colours, and the Source of Colour in the Prism. 

 By Walter Crum, Esq. Glasgow. 8vo, pp. 47. 



This treatise is intended to shew, that darkness is the source of colour, 

 and that primary colours are only three in number, — yellow, red, and 

 blue. We recommend the ingenious author to peruse the Farhmlehre 

 of the celebrated Goethe, who has long ago shewn darkness to be, in 

 truth, the soiu-ce of colour, and secured the general reception of the 

 same opinion in Germany. 



List of the Works, and Memoirs of J. Raddi, an Italian 

 Botanist. * 



1. On the new species of Mushrooms found in the neighbourhood of 

 Florence, and not described in the Systema Naturce of Linnaeus, 

 Edit. XIII. (Inserted in Vol. XIII. of the Actes de la Soc. Ital. 

 des Sciences. Modena, 1806; with five coloured plates.) 



* An esteemed correspondent having suggested to us the utility of our collecting 

 together the titles of works and papers of eminent naturalists, as opportunity may 

 offer, we commence an intended series of such catalogues with the above List. — Ed. 



