314 Eazards of Cashau.—Almospheric Phenomena. 
on the Ist of March 1822, from the ship Ospray, of Glasgow, 
which sailed from Greenock on the 20th day of February 1820, 
on a trading voyage round the world. Whoever finds this is re- 
quested to insert a notice of the time and place in some literary 
or political publication, with the view of establishing facts re- 
lative to the currents of the ocean: 130 days from Calcutta, re- 
turning towards Greenock—* All well.’ 
‘© ALEXANDER M‘GILL, Master.” 
LIZARDS OF CASHAU. 
“¢T observed numbers of lizards and tortoises crawling along 
the sides of the road. Some of the former were of strange shapes, 
and others of unusual length; one that we found dead, was above 
two feet from the nose to the tip of the tail. I remarked that 
these animals invariably took the colour of the ground on which 
each particular kind existed. If verdant, the lizard was green ; 
if sandy, she was yellowish white; if red earth, or reddish moulder- 
ing stones, she was pink; and if found among fragments of rock, 
and other dusky hued relics, she would appear of a varied brown. 
I leave this fact to naturalists to explain, confessing myself to- 
tally ignorant of its secret.”—Sir Robert Ker Porter. Travels, 
vol. i. p. 390. oe 
ATMOSPHERIC PHENOMENA. 
To the Editor. 
Sir,—The large halo so frequently seen in particular states of 
the atmosphere, at the distance of about 22 degrees from the ap- 
parent disk of the sun or moon, has been very properly called the 
opprobrium philosophorum. Newton himself, who so satisfac- 
torily solved the phenomena of the rainbow by the principle of 
ordinary aqueous refraction, and those of the smaller haloes or 
corone by that of refraction through thin strata, acknowledges 
that the great halo is of a distinct kind. He could only explain 
it by falling in with the idea then prevalent, that it was produced 
by refraction through a horizontal stratum of hail or snow; a 
notion which has been regarded as very doubtful, from consider- 
ing both the great variety of atmospheric temperature at which 
this appearance occurs, and the very peculiar structure which, 
on calculation, it has been found necessary to attribute to the 
floating icy particles. 
A late writer has advanced as an hypothesis, that the refrac- 
tive power of particles of vapour sufficiently small for permanent 
floatage in the atmosphere is’ diminished by the attraction of the 
air; an hypothesis by no means improbable, since the efficacy of 
the attraction in question follows the inverse ratio. of the dia- 
meter of the particle, 
Poss ibly 
