Miscellanies. 367 
pared was fully ascertained and acknowledged. On the evening of 
the 25th of May, when there was no moon light, and the night dark, 
with occasional showers, the appearance of the light viewed from 
Blackwall, a distance of ten miles, was described as being very splen- 
did. Distinct shadows were discernible, even on a dark brick wall, 
though no trace of such shadows could be perceived when the other 
lights, consisting of seven reflectors with Argand lamps, and the 
French lens, were directed on the same spot. Another striking and 
beautiful effect peculiar to this light was discernible when the reflec- 
tor was turned, so as to be itself invisible to the spectator. A lon 
stream of rays was seen issuing from the spot where the light was 
known to be placed, and illuminating the horizon to a great distance. 
As the reflector revolved, this immense luminous cone swept the hor- 
izon, and indicated the approach of the light long before it could it- 
self be seen from the position of the reflector. ‘These effects, how- 
ever, on a moon-light night, or in hazy weather, cease to appear.— 
Ibid. 
4. Original decomposition of Potash.—Dr. Paris, in his interest- 
ing biography of Sir Humphrey Davy, after giving an account of the 
preliminary experiments which led to the final and most successful 
result, has taken from the manuscript Journal of the Laboratory of 
the Royal Institution, a fac-simile of the minute, in Davy’s hand writ- 
ing, of the successful experiment of October the 19th, 1807. It is 
highly interesting and characteristic, but it should have been accom- 
panied by the substance of it in print, (say the reviewers,) for it is 
not every one who will be able to decipher it. It ransthus— _ 
“Oct. 19. When potash was introduced into a tube, having a 
Platina wire attached to it, and fixed into the tube so 
as to be a conductor, i. e. so as to contain just water 
fnough, though solid, and inserted over mercury, 
When the platina was made negative, no gas was form- — 
ed, and the mercury became oxidated, and a small quantity of the 
alkaligen was round the platina wire, as was evident from its quick 
inflammation by the action of water. When the mercury was made 
the negative, gas was developed in great quantities from the positive 
Wire, and none from the negative mercury, and this gas proved to be 
Pure Oxycen.—Capitan Experiment, proving the decomposition 
i 
of Porasy.” 
