Retrospective Criticism. 189 
Coquimbo owl, being two very different animals, are, in the heading, stated 
to be one and the same thing. The passage quoted relates to the Biscacho, 
an animal described by Captain Head as resembling a rabbit, but which, in 
the passage I allude to, is called “a bird”’? The description runs through- 
out of the Biscacho, but the drawing is that of the owl.— AZ. January, 
1830. 
The Aerial Spider, — Sir, My devotedness to experimental electricity, for 
the last fifteen years, should certainly, at any rate, have gained for me the 
requisite qualification for investigations like these, and I therefore cannot 
cede to an assertion evidence gained through the medium of experiments 
diligently and carefully conducted. Atmospherical electricity has been with 
me a favourite study, and I trust it is one in which I find myself in some 
desree at home; and the employment of Coulemb’s Balance of Tarsim, 
with Breguet’s Thérmomélre métallique, has been of essential service to me. 
Professor Brande has justly concluded that the divergence of the threads 
in the fasciculi represented by Mr. Bowman’s diagram can scarcely be 
otherwise explained ; and a very slight excess of electricity in the excited 
substance employed as a test for the electric condition of the thread, every 
electrician knows, would defeat the end proposed. Is Mr. Blackwall aware 
of this, and have his experiments been thus secured? A spider’s thread, 
darted through the air, must necessarily acquire electricity from the friction 
occasioned by its impulse through that medium ; and, if propelled counter to 
a current, the amount of excitement will be greater; a thread of glass is 
excited under such circumstances. Is Mr. Blackwall ignorant that a current 
of air is an excitant of electricity ? a fact long ago proved by Bennet and 
other electricians. The air issuing from the nozzle of a pair of common bel- 
lows, and directed on the cap of the electroscope, will occasion a divergence of 
its pendent leaves. Now, Mr. Blackwall should have known all this: and, 
permit me to ask, what connection is there between heated currents emanating 
from the earth and an impulse of air, even on Mr, Blackwall’s own showing ? 
I am not disposed to yield to Mr. Blackwall in electrical experiment ; and 
those who have witnessed my illustrations of this branch of science will rea- 
dily, if I mistake not, give me credit for successful and delicate manipulation. 
I am in possession of attestations, from other sources than my own, in veri- 
fication of the asserted fact of the short-lived term of existence, in the case 
of the dark-brown glossy gossamer spider, when imprisoned within narrow 
precincts, as a small chip box, or tube of glass; and I would just say to 
others (certainly not Mr. Blackwall) experimentum jiat. Ihave found the 
result, in nearly twenty cases, with this variety, and have not made the 
experiment with any other. The “ shy retiring truth,” however, gleams in 
his own account of the matter; though 
“ He that’s convinced against his will, 
Is of the same opinion still,” 
If my antagonist can satisfactorily confute the facts and phenomena 
. fr) es J * 3 5 
recorded in the volume referred to, he is a more profound wit than I 
have hitherto given him credit for. This notice, however, is jizal on my 
part. Mr. Blackwall may continue his appeals to the Council of the Lin- 
nean Society, or to the individual authority of Humboldt: I protest, how- 
ever, against being esteemed accessary to any opinion that would suppose me 
to think by proxy. Lam, Sir, &e.— J. Murray. Nov. 19, 1829. 
Mr. Palmer of Chigwell’s Lists of Plants. — Sir, In reading your last Number of the Magazine of 
Natural History, I must beg leave to say, I was rather surprised to see, among the plants collected 
by the Rev. S. Palmer of Chigwell, Essex, many that are, I believe, every where almost, in this 
country, of very common occurrence. Localities of sach plants, I humbly conceive, cannot be of 
any service. Thymus Népeta is mentioned, and marked with a star, as being rather uncommon, 
while Verdnica spicata, certainly a much more local plant, is not so distinguished. If ever found 
in Epping Forest, it certainly merits a locality being given. Antirrhinum £latine is mentioned as 
being common in ditches in the neighbourhood of Chigwell. Bya ditch is generally meant an 
excavation with water in it ; but the plant in question is found almost: exclusively in cultivated 
