Fune 23, 1870] 
NATURE 
I4I 
LETTERS TO THE EDITOR 
[ The Editor does not hold himself responsible for opinions expressed 
by his Correspondents. No notice is taken of anonymous 
communications. | 
The Corona 
HAVING been informed that my remarks at the meeting of 
the Royal Astronomical Society, on Friday last, have been 
interpreted otherwise than I meant, doubtless in consequence 
of my having spoken without preparation, I beg to repeat what 
I intended should have been the purport of my statement. 
It seems to me beyond reasonable doubt that we have upon 
all the photographs, whether of long or of short exposure, 
a representative of something which is at the sun, since the con- 
tour of the radiance depicted upon all the photographs exhibits 
minima, in directions closely approximate to the extremities of 
the sun’s axis of rotation. - Furthermore, exterior to all this, 
and apparently masking it in a very great degree to the ordinary 
observer, isa much wider and more conspicuous radiance of very 
irregular outline, to which the name Corona has been ordinarily 
applied, The streamers and irregular projections of this latter 
~ corona. appeared to me to vary in position during the period 
of totality in August last. They seem, moreover, to have no 
connection with the positions of the prominences, nor yet with 
that of the solar axis, and hence I infer that this phenomenon 
arises from something which zs not at the sun. 
London, June 15 B, A. Goutp 
Euclid as a Text Book 
I HAVE been waiting in the hope that Mr. Levett’s letter 
(Nature, No. 30, pp. 65, 66) would elicit a response from other 
members of the ‘frank and file” of mathematical teachers. No 
one having come forward, I venture to do so, lest the subject 
should again drop. Mr. Levett’s suggestions appear to me at 
least worthy of some little ventilation, and I hope some leader 
will be induced to utter a note on the subject. Knowing that 
many of the leading geometers of this country are favourably 
disposed to the ‘‘reform” movement, I feel sure their silence is 
not attributable to indifference. In the meantime it is my opinion 
that no isolated efforts will bring about such a reform as will 
thrust out Euclid from our schools; united action is what is 
wanted, and then “a long pull, a strong pull, and a pull all 
together.” I could easily select from the four Universities of 
Oxford, Cambridge, Dublin, and London, four geometers who 
could, I believe, if it be possible, bring out in concert a work 
which should be a fitting rival of the old-world geometry, com- 
mand the attention which such a work ought to secure to effect 
the change desiderated, and convince gainsayers. A scheme 
might be drawn up in concert, the working out of the details 
committed to one, and the work appear under the united names 
of the body. Then as to the number of the ‘‘rank and file” 
willing to give their support to such a plan, possibly some 
mathematical master at one of our public schools (I could in 
this case also make a selection) could give much valuable in- 
formation. I hazard the above remarks, not wishing the ball 
set rolling in the columns of NATURE to come to rest, until the 
change has been effected or its inexpediency irrefragably demon- 
strated, valeant quantum valent. hk. TUCKER 
University College School, June 11 
The Interior of the Earth 
UNDER the signature of Z., I find in your issue of the 16th 
inst., a short notice of ‘*‘ The Interior of the Earth.” A clerical 
error made during the Epsom or Ascot races, such as F.L. instead 
of E.I., is excusable, though not comprehensible ; a misquotation 
which he has made may be pardoned, but a misrepresentation 
purely from neglect of reading is quite unbearable. We tells 
your readers that I proceed “‘to explain the earth’s heat and vol- 
canic phenomena by a like action on buried vegetable matter. 
If he had read p. 33, he would have found that to the cause 
alluded to ‘I partly assign the changes which have taken place 
in the strata connected with our coal pits.” Z. thinks that a pe- 
rusal of Lyell’s “ Principles ” would have stopped the writing of 
my book, I beg to tell him, that this work was the first that 
convinced me of the great geological error which I have exposed. 
Z. does not seem to have read my reasons for using Page as my 
text-book ; I hope he is not hurt at being left out himself, but it 
Thad quoted from all the books I have read on the subject, I 
| should have been as unintelligible as some of them. 
A sneer is not a review, but if Z., or any one else, can prove to 
me that an internal and inherent heat within the earth has 
caused, or does cause, the phenomena alluded to, I will with 
pleasure renounce my present creed ; but, till then, I merely say 
thatas I have controverted the theories of others, I shall be glad 
to read any controversions of my book, if written in the same 
spirit of inquiry. H, P. Mater 
Prismatic Structure in Ice 
THE enclosed letter, which has just reached me from Canada, 
seems to me so interesting that I venture to hope a place may 
be found for it in the columns of Narure. I may, however, 
state that I still adhere to my conviction that the vertical chains 
of air bubbles are the consequence of the prismatic structure ; 
since in all the cases I have seen they are too regular to have been 
formed as my correspondent suggests. Although I believe it is 
an established fact that, speaking generally, ice contracts with 
cold, Iam not aware that its demeanour ata temperature of about 
32° F. is quite so accurately ascertained; it seemed to me, 
when investigating what had been written on the subject, that 
further information was needed on this point. The prismatic 
structure appeared, and still appears, to me inexplicable on any 
other theory than that of contraction. 
St. John’s College, Cambridge T. G. BonNEY 
‘“Tn one of the March numbers of Nature I see a letter over 
your signature on the prismatic structure of ice, and as our climate 
gives us favourable opportunities of observing this and other 
curious facts respecting ice, I am induced to address a few words 
to you on the subject. 
“* The ice on our inland lakes is generally two or three feet thick. 
As the spring advances, an inch or two may be melted away from 
the lower surface, and somewhat more from the upper one, but 
the thickness is not materially reduced until its final disappear- 
ance, The first sign of the approaching break up is that the 
ice becomes dry, from the prismatic structure having commenced 
to show itself, allowing the surface-water to percolate through 
the interstices ; itis then said to be honey-combed. In this state 
the lower layers of transparent ice are still solid, though if you 
cut cut a block the prismatic structure is very evident ; but the 
upper portion, which has been formed from a mixture of snow 
and water, readily breaks up under your feet into little granules of 
ice. The next stage is that the ice becomes black, showing that 
it is soaked as it were with water; and if at this time there is 
any open water, as wherea river falls into the lake, and wind 
enough to create a swell, the whole surface of the ice may be 
observed to undulate. Even then, sometimes, a single night’s 
frost may make all firm again, and you may even trust horses 
upon it. If the ice now breaks up prematurely with a high 
wind, it becomes a mass of spiculae of ice which have not 
reached the melting point, and which I have seen accumulate to 
the depth of six or seven feet against the edge of the ice, which 
has not yet broken up. But if there is no wind, the whole sur- 
face of the lake may appear an unbroken sheet of black ice, 
still a couple of feet thick, till, in an astonishingly short space 
of time, sometimes not more than a few minutes, it disappears 
as if by magic. So sudden is this disappearance, that the ice 
is popularly believed to sink. 
‘**T once had a very good opportunity of noticing this sudden 
disappearance. I had built on the ice during the winter a 
pier of logs filled with stones, and when the spring came, it 
settled down to the bottom, carrying with it a large cake of the 
ice. When the lake had opened, I went round the pier in my 
canoe to seeif it had settled evenly. There at the bottom, in 
six or seven feet of water, lay the cake of ice it had carried 
down, with the chips still imbedded in it which we had made 
in building the pier ; and, as I looked, blocks would break off 
of a foot or more in thickness, rise to the surface, break up into 
spiculze, and almost instantaneously disappear. 
“*T quite agree with you that these prisms have no connection 
with the hexagonal form of ice crystals, but I doubt your expla- 
nation that they arise from the contraction of the ice as it 
approaches the melting-point. Does ice contract under such 
circumstances ? Although water expands in freezing, and, vce 
versa, occupies less bulk when reconverted into water, yet, 2s 
long as it remains ice, I conceive that it contracts with cold and 
