Oct. 19, 1871] 

British Mosses 
Nor having noticed in the last number of Nature, Oct. 12, 
any correction made by either the Rev. Mr. Berkeley or Dr. Dickie, 
of a statement made by the former gentleman in the previous 
number, Oct. 5, which, as it reads, is calculated to lead to error, 
if left unnoticed, I send you this note. 
In the short paragraph at p. 446, ‘“‘ Notaris on Mosses,” Mr. 
Berkeley, in correcting a previous omission having reference to the 
genus Habrodon, states that Conomitrium julianum had been 
sent to Dr. Dickie by Mr. Wilson from his district,” Warrington. 
This being only one side of the truth, I take the liberty of supply- 
ing the other side. Any person reading the paragraph as it 
stands would certainly suppose that this very elegant, and very 
remarkable moss was a native of the Warrington district, which 
it is not, nor of any other part of the British Isles that 1am aware 
of. No doubt Dr. Dickie received fresh specimens of the moss 
from Mr. Wilson at Warrington, as I also did, but they were of 
foreign origin, and only cultivated by Mr. Wilson in his little 
conservatory at Warrington, where he had them placed in a large- 
mouthed jar filled with water, in which condition I saw the 
plants during the month of October, 1870, on the occasion of the 
last visit I paid to my now departed friend. 
I may further remark that I had been led to suppose it was 
Dr. Schimper, of Strasburg, who first made known the genus 
Habrodon to be British, In the summer of 1865 he and the 
late Mr. Wilson paid mea visit at Dublin, and after leaving 
Treland, Dr. Schimper accompanied a party to the Highlands of 
Scotland, on which excursion the Habrodon was discovered 
growing on trees near Killin, whence I have specimens from the 
party, which were collected on that occasion. 
Glasniven, Oct. 16 D. Moore 

Corrections 
A PARENTHETICAL passage in my ‘‘ note on the Cycloid” has 
been transposed. Instead of ‘‘ (a luminous point for the nonce) 
the sun in the meridian,” &c., it should have been ‘‘the sun (a 
luminous point for the nonce) in the meridian,” &c. 
In Mr, Abbott’s paper on 7 Argus and its surrounding nebula 
there occurs the statement that I consider ‘‘an increased or 
decreased distance in space may account for the fluctuations of 
thenebula.” I have never suggested such an explanation. 
What I have said is that the fluctuations, if real, would seem to 
suggest that the nebula has not those inconceivably vast dimen- 
sions which would correspond to the vast distance once assigned 
to it. My opinion was (and is), ofthat the nebula is nearer 
than it was formerly, but that it is nearer than it was formerly 
supposed to be, RIcHD, A, PROCTOR 
A Universal Atmosphere 
WILL you permit me ‘to ask Mr. Mattieu Williams how, on 
his hypothesis, ‘‘that the atmosphere is universal, and that each 
planet attracts to itself an atmosphere in proportion to its mass,” 
he accounts for the well-known fact that the moon shows no signs 
of an atmosphere sufficient to produce any indication of refraction 
during the occultations of a star? 
I think Mr. Williams’s book deserves far more attention than 
it has received, so I trust I shall be acquitted of any wish to 
indulge in carping criticism. JOHN BROWNING 
111, Minories, October 10 

The Temperature of the Sun 
HAvinG been absent from home I have but just seen Mr. 
Ericsson’s article on the ‘‘Temperature of the Sun” in 
Nature, (No. ror, p. 449. All who feel an interest in the 
subject must be indebted to Mr. Ericsson for the experimen- 
tal evidence which he has contributed to the investigation, 
and for such further light as his ingenuity will doubtless enable 
him to throw upon it ; but few, I think, will be inclined to admit 
that the reasoning advanced in his recent article justifies in any 
degree the inferences which he has there drawn. 
At the outset of the inquiry it does not seem very likely that 
we shall gain much correct knowledge of the condition of the 
solar atmosphere by inquiring what that condition would be if it 
were replaced by a medium similar to the terrestrial atmosphere, 
and containing the same quantity of matter for corresponding 
areas of the spherical surface, If the casé were otherwise it 
would be necessary to point out that Mr. Ericsson’s numerical 
results are vitiated by his omission to consider that the volume of 
NATURE 


487 
a sphere varies as the cube of the radius, and therefore that on 
the data assumed by him the earth’s atmosphere raised to the 
temperature of the solar surface, instead of attaining a height of 
279,006 miles, would barely reach to one-twelfth of that limit. 
But I may further remark that the assumptions on which Mr, 
Ericsson’s calculations are founded are open to many objections. 
It is far from certain that the direct proportion between the in- 
crease of volume of gases at constant pressure and the increase of 
temperature, holds good for an enormously high temperature 
such as prevails in the solar atmosphere, and it is certain that 
the resistance offered by that medium to the passage of radiant 
heat depends not solely or mainly on its temperature, but on its 
chemical—z.¢. its molecular—constitution. 
It may further be noted that Mr. Ericsson’s experiments on the 
diminution of heat emanating from a disc of incandescent iron, 
according to the angle at which its face is inclined to a fixed 
thermometer, do not justify similar conclusions with regard to 
heat emanating from a mass of incandescent gases or vapours, 
At the same time it may be regretted that Mr. Ericsson has not 
given fuller details respecting the experiments in question, which 
may give valuable results irrespective of the conclusions to which 
he has applied them, JOHN BALL 


Flight of Butterflies 
CAN you tell us where the yellow butterflies are going? 
About ten days since, while chatting with several gentlemen 
at the Jackson Sulphur Well about caterpillars, one of them re- 
marked that the worm was about, for, says he, the yellow butter- 
flies are all going east. 
We thought at first he was telling us a “‘ fish story”, but soon 
became convinced that he knew whereof he spoke, for while we 
sat there a great number of bright-coloured, medium-sized butter- 
flies came by us, all winging their way towards the rising sun. 
Now, we do not think that this fly is related to the caterpillar, 
for the moth that lays the egg of that destructive wormis a very 
different fly ; nevertheless it is a singular fact that they are all 
going east. 
I have been at several different points since leaving Jackson, 
and at every place they fly the same way. Can you tell us 
whither they go? Perhaps if you will ask the question in your 
widely-circulated journal, some naturalist, or somebody over to 
the eastward, may tell us where they rest. ALA 
Mobile, Sept. 6 
[A similar fact will be found recorded in our ‘‘ Notes” re- 
specting the Urania leilus.—ED. |] 

Velocity of Sound in Coal 
THIs is a very interesting subject, at least to those who have 
anything to do with coal mines. And yet I have not met with 
anything that points to it, nor any formula whereby it might be 
calculated. But perhaps this is a subject to which the attention 
of physicists has not been drawn. I have been told that blast- 
ing has been heard at the distance of 150 yards underground, 
and I have heard the signals of the colliers, z.¢., by hitting the 
surface of the coal with one of their tools, at the distance of 
fifty or sixty yards, and have also heard the shouts of the men at 
the distance of fifteen yards ; but I have never met any person 
who could give the velocity, nor seen any book on physics in which 
there is anything concerning it. But perhaps it is a very hard 
subject to deal with from the difference of the specific gravity of 
the coals, and also the different temperatures that we meet there. 
And if from these different causes it would be hard to find the 
real velocity, yet by calculating a velocity that might be rather 
theoretical at first, we might by degrees come nearer the truth. 
D. JosEPH 
Ty Draw, Pontyfridd, Oct. 5 

Prof, Newcomb and Mr. Stone 
I Am obliged to Mr, Lynn for pointing out that the statement 
by ‘‘P. S.” was contradicted. I had not been aware of this, 
It never occurred to me to doubt either the authorship or the 
authenticity of the statement. I cannot tell how it chanced that 
‘“W. T. L.’s” response escaped my attention. Perhaps I never 
saw the January number of the Astronomical Register; or, 
perhaps, a variety of other reasons which would not interest your 
readers, 
