528 PHILOSOPHICAL TRANSACTIONS. [anNO 1721. 



Often as I have viewed seeds, for several years past, with the microscope, 

 yet I never imagined, that the little cells were endued with so many vessels, 

 though I have frequently considered, how the intrusion of the particles of the 

 meal, or flour, into the membranes was effected; nor should I ever have 

 attained to it, but by continual labour in the investigation of things which are 

 concealed from our naked eyes. 



An Account of some Experiments relating to Magnetism. By Dr. Brook 



Taylor. N*" 368, p. 204. 



After having given an account of an experiment made with the large magnet 

 in the Repository of the Royal Society, described in N° 344, the Doctor further 

 proceeds on the same subject as follows. If it were known what point within 

 the stone, and what point in the needle are the centres of the magnetical power, 

 it would be easy to find the true powers of the magnet at all the distances 

 observed. For want of that knowledge, I have computed the forces from the 

 centre of the needle, and the extremity of the loadstone, and find, that at the 

 distance of 9 feet, the power alters faster than as the cubes of the distances; 

 whereas at the distances of 1 and 2 feet, the power alters nearly as their squares. 

 To try whether the law, by which the magnetism alters, could be reduced at 

 all distances to any one certain power of those distances, I sought those points 

 in the needle and stone, which being used as the centres of the power, might 

 have that property. But in that case I found the centre of the stone must be 

 carried quite out of its figure, to make the distances large enough for this 

 purpose. From whence it seems to appear, that the power of magnetism does 

 not alter according to any particular power of the distances, but decreases 

 much faster in the greater distances than it does in the near ones. 



This seems to be confirmed by other experiments I made. The first ex- 

 periment was thus: I made a needle \ of an inch long, of very fine steel-wire, 

 a foot length of which weighed only a grain, which I lengthened by sticking a 

 light piece of rush to it, so that I could observe the direction of the needle 

 in all the trials with a radius of 2 inches. Instead of a magnet, I used a 

 touched needle of steel-wire, which I set on a perpendicular to the horizontal 

 plane I made the observations on, by means of a frame made to transport it 

 from one place to another ; the north end of the needle being placed down- 

 wards, and made a little sharp, that it might mark the paper it was set upon in 

 every position, by pressing the top of the needle gently with the finger. The 

 observations were made in this manner: after having taken notice of the natural 

 direction of the small compass needle, I brought the perpendicular needle as 

 near to it as conveniently it could, setting it in such a manner, that a line from 



