Aug. 18, 1870] 
single bright colour, scarlet for instance, a kind of shadow ap- 
pears to come over any part of the surface to which I direct 
the eye. 
With respect to my absolute power of perception of colour, I 
believe that though I cannot be said to be colour-blind, my eyes 
are less sensitive to colour than the average of those who have 
equally good general sight. For instance, scarlet and green do 
not appear to present to me the same degree of contrast that they 
do to most persons with whom I have made the comparison. 
Close at hand the contrast is sufficiently vivid, but a scarlet 
uniform seen at some distance in a green field would not 
attract my attention by contrast of colour, though I could 
make out the difference under a favourable light when my 
attention had been called to it; so also the scarlet berries 
of the mountain ash would at a little distance attract my 
notice rather by their form than by their colour, especially if 
seen against the sky or a bright object. Again, I can never 
pronounce with certainty as to the colour of distant bright lights; 
the colours of the lights, for instance, used for railway signals, 
though distinctly enough perceived by me when close at hand, 
puzzle me much when seen at a distance, while I am quite in- 
capable of assigning with certainty a colour to a star or a metecr. 
I should add that my ordinary power of vision is good ; 
though here my right eye has a slight, but unmistakeable, ad- 
vantage as to distinctness over my left. Hence, in looking at a 
brilliantly-coloured picture I have found that I could appreciate 
the drawing best with my right eye, the colour with my left, 
while in using both eyes each appears to remedy the defect of 
the other. 
I think that the facts which I have here stated cannot fail to 
be of interest to those who are inclined to theorise on the nature 
of colour-blindness ; but apart from all theory it would be satisfac- 
tory if the statement of my case should induce others to examine 
their own perceptions of colour with each eye separately, and in 
the event of their observing anything confirmatory of, or con- 
trasting with, my observations, to send an account of them to 
Nature. I think it quite possible that such cases may not be 
very uncommon, since the defect is one which may easily escape 
the notice of the subject of it. 
Harrow, August I Rosert B. HAYWARD 
The Source of Solar Energy 
Mr. Gree still misses my meaning. I do believe that meteors 
supply a portion of the solar energy, and I also believe that they 
fallin enormous quantities into the sun ; what I do not believe 
is that the whole solar energy is derived from meteors, or that 
any meteors fall ina solid state upon the sun (whose surface is 
also certainly not solid, even if any part of his mass be). 
Mr. Greg’s reasoning only proves what I have already pointed 
out, that none of the meteor systems our earth encounters can 
supply a meteoric downfall on the sun. This is, however, so 
obvious as to need no enforcing. 
The reasoning by which I show that enormous quantities of 
meteors must fall upon the sun is wholly untouched by Mr. 
Greg’s arguments, and is, so far as I can see, simply incon- 
trovertible. 3 
Surely Mr. Greg is not in earnest in saying that there would 
be a loss of solar energy if a large mass of iron fell on the sun 
before it was quite melted (any conceivable mass would, by the 
way, be vaporised), decause the sun would have to melt the por- 
tion which remained solid. That solar energy would be con- 
sumed in the process is true enough ; but if Mr. Greg supposes 
that the total solar energy would be diminished, he altogether 
misapprehends the whole subject he is dealing with. If the 
action of the solar energy in changing the condition of matter 
forming (as the imagined meteorite would) part of the sun’s sub- 
stance had to be counted as loss of energy, the sun would be 
extinguished in a very short time indeed. Such processes involye 
exchange, not loss. 
If the earth could be placed on the sun’s surface, the action of 
the sun in melting and vaporising the earth, and producing the 
dissociation of all compound bodies in the earth’s substance, 
would involve an enormous expenditure of energy, yet the solar 
energy, considered as a whole, would be recruited, even apart 
from the fact that the earth would serve as fuel. The absolute 
temperature of the sun would, I grant, be diminished in this 
imaginary case, though quite inappreciably, but his total heat 
would be increased by whatever heat exists in the earth’s sub- 
stance. 
NATURE 
315 
Apart from this, however, if the minimum velocity with which 
a meteor or other body can reach the sun, is such as would—if 
wholly applied to heating the body—completely melt it, then 
the size of the body makes no difference whatever in the result. 
The meteor might not be melted if enormously large, but in that 
case the balance of heat would be communicated to the sun. In 
reality, of course, the heat correspondining to meteoric motion 
near the sun is very far greater than is here implied. 
But I really must apologise for bringing before your readers 
considerations depending on the most elementary laws of the 
conservation of energy. RICHARD A, PROCTOR 
Muller's Physics and Meteorology 
From Prof. Jack’s Review of Miiller’s ‘* Physics and Meteor- 
ology,” in your issue of August 4, Linfer that he is not aware that 
an earlier edition of that valuable book was translated into English 
more than than twenty years ago, and formed one of the volumes 
of Bailliere’s Sctentific Library. M.A. Cant. 
Aug. 7 
Colour of Water 
Mr. E. R. LANKESTER, in his letter in NATURE on 2Ist July, 
does not mention what is certainly one of the most remarkable 
known instances of a decided colour in water, I mean the Blue 
Lake near the road from Frutigen to Kandersteg in Switzerland. It 
is very small, not a stone’s throw across. I think it is fed by 
springs. Its blue tint is so decided as to give the idea of some 
colouring stuff mixed with the water—not that it can be 
really so. 
The Lakes of Neufchatel and Bienne are of the same light- 
green tint as those of Lucerne, Brientz, and Thun, although the 
latter are fed by glacier streams and the former are fed by the 
streams of the Jura, where there are no glaciers. This appears 
to prove that the solid matter which glacier streams contain in 
suspension can have nothing to do with causing the green tint of 
most of the Swiss lakes. Jos—ErpH JOHN MURPHY 
Old Forge, Dunmurry, Co. Antrim, Aug. 5 
Water Analysis 
Your article entitled ‘* Water Analysis” consists ot a review 
of a book, a commentary on a paper, and the reviewer’s opinions 
of the character of Mr. Chapman and myself. 
I shall not trouble you with any rectification of the statements 
contained either in the review or in the commentary on the 
paper ; inasmuch as both the book and the original memoirs are 
accessible to the readers of NATURE, and the entire subject has 
already been very fully discussed. 
In giving his opinion on the character of the authors of the 
book, the reviewer ‘‘deplored that two young chemists, with 
such undoubted abilities as Messrs Wanklyn and Chapman pos- 
sess, should have rendered themselves notorious by attacking 
older workers in scientific investigation.” 
Perhaps you will allow me to say, that in rendering ourselves 
notorious in this manner, we have committed no crime, and that 
I cannot see why it should be deplored. 
I believe that a great deal of the work which these older 
workers have done is unsound, and have endeavoured to sweep 
away some of that which I believe tobe unsound. In this sweep- 
ing [ have been to some extent successful, successful to an un- 
comfortable and alarming extent, I suppose your reviewer would 
say. But, if the rottenness of much that passes current in 
science is appalling, it is surely matter for congratulation that 
there are young men who will undertake a crusade against it, 
eyen at the risk of incurring the disapprobation of the older men, 
and of suffering every wrong that the possession of place and 
power enables these older men to inflict. 
London, Aug. 14 J. ALFRED WANKLYN 
{Mr. Wanklyn omits the sentence following his quotation :— 
“Tt is, no doubt, very laudable ina young and ardent investigator, 
when he points out that high authorities may err, and frequently 
have erred, but the manner in which these gentlemen have 
carried out their corrections has made their matter more distaste- 
ful.’—Ep. ] 
Suckers from the Apple Tree 
Most of the orchards in the west of Herefordshire have had 
their herbage injured during the present season by the extra- 
ordinary profusion of suckers thrown up by the apple-trees. In 
