id'l PHILOSOPHICAL TRANSACTIONS. [aNNO IJAO. 



bottom of the stalk, c, a branch with the umbels of flowers in different states. 

 d, an interior view of the flower of its natural size, e, a posterior view of the 

 same, f, the anterior appearance of the flower through a microscope, g, the 

 posterior view of the same, h, a view of the rudiments of the fruit after the 

 decay of the flower, i, the same magnified. 



Explanation of fig. 12, pi. 6, representing the cicuta aquatica of Wepfer.* — 

 a, a branch of this plant .with its umbels of flowers in different states, b, the 

 appearance of the bottom of the stem, growing from the crown of the old root, 

 c, an interior view of the flower of its natural size, d, an interior view of the 

 same magnified, e, a posterior view of the flower magnified, f, the vasculum 

 seminale, and seed, g, the same magnified. 



. Explanation of fig. 1, pi. 7, representing the root of the cicuta aquatica in 

 winter, a, the rudiments of the leaves, b, the old rotten root not yet sepa- 

 rated from the new one of the preceding summer, c, a longitudinal section of 

 the root exhibiting the cells. 



ji Letter to Mr. Benj. Robins, F.R.S. showing that the Electricity of Glass dis- 

 turbs the Mariners'" Compass, and also Nice Balances. N° 480, p. 242. 



While so many gentlemen are labouring to find out the uses of electricity, it 

 has been my fortune to discover one of the inconveniencies attending that pro- 

 perty in glass. 



Having lately had occasion to compare together two compasses of a different 

 make, the one having a bare needle, as usual, and the other a chart, in the 

 tnanner that mariners' compasses are commonly made, I happened to wipe off 

 with my finger some dust, which lay on the glass of the former ; and thus put 

 the needle, which was before at rest, into a violent disorderly motion, partly ho- 

 rizontal, and partly vertical or dipping. After several repetitions of the same 

 thing, I found that the glass, by so slight a touch, was at that time excited to 

 electricity, so far as to disturb the needle extremely. 



The same glass being rubbed a very little more with a finger, or a bit of mus- 

 lin, or of paper, would attract either end of the needle, so as to hold it to the 

 glass, for several minutes, far out of the due direction, according to what part 

 of the glass was most excited. And when the needle had for some time adhered 

 to the glass, and afterwards dropped loose, and made vibrations, those vibra- 

 tions would not be bissected, as usual, by that point where the needle should 

 rest, but either be made all on one side, or be very unequally divided, by means 

 of some remains of electrical virtue in that part of the glass which had attracted 

 the needle; till, at length, after 15 minutes or more, all the electricity being 



* Cicuta virosa Linn. 



