) Be ahd 
ert 
Pte 
Sept, 11, 1873] 
known species, with notes of their distinguishing charac- 
ters and geographical distribution. One of the most rare 
and interesting species figured (in Part 20) is the Teydean 
Chaffinch, a bird of a blue colour, and which is confined 
to the upper limits of the pine forests of the Peak of 
Teneriffe, and to the desolate plains above them, feeding 
on the seeds of the Retanca (a broom-like plant) and the 
Adenocarpus frankenoides, which characterise those re- 
gions, as well as on the seeds of Pinus igo 7 
Lehrbuch der Physik, von Dr. Paul Reis (Dritte Lie- 
ferung). Leipzig: 1873. 
Tuis forms the concluding part of Dr. Reis’s useful hand- 
book of Physics. The subject of physiological optics is 
continued, followed by a description of optical instru- 
ments and the laws of the interference and polarisation of 
light. Heat is treated in the next part, but hardly so fully 
nor so well as light ; radiant heat, for example, occupying 
less prominence than it deserves. Considerable space is 
devoted to the explanation of machines for the conversion 
of heat into motive power: thus we have some of the 
various forms of steam-engine described, together with a 
full account of Ericson’s heat-engine and Lenoir’s gas- 
engine. Magnetism follows heat, and then we come to 
static and dynamic electricity and the practical applica- 
tion of electricity. The book closes with a few chapters 
devoted to the physics of the heavens, or in other words 
a brief sketch of popular astronomy and meteorology. The 
principal defect of this handbook is the want of sufficient 
woodcuts to illustrate the apparatus referred-to. The 
whole work exhibits the characteristic solidity and 
thoroughness of the German race, and is a marked con- 
trast to some of the recent French popular text-books on 
Science, the profuse and beautiful illustrations in which 
almost supplant the letterpress. Let us flatter ourselves 
that in our nation these complementary races inter- 
mingle. 
LETTERS TO THE EDITOR 
[Zhe Editor does not hold himself responsible for opinions expressed 
by his correspondents. No notice is taken of anonymous 
communications. | 
Tyndall and Forbes 
Ir will probably be considered necessary that Dr. Tyndall’s 
pamphlet, * which first appeared as an article in the Contemporary 
Review, be answered at full length. That, however, cannot be 
decided for some time, as several of those concerned are abroad ; 
but it may be well to let Dr. Tyndall know at once that there 
is no difficulty whatever in answering him, and that the answer 
will not lose force or point by a littledelay. In the meantime I 
hope you will give me space to briefly notice a few of the more 
obvious inconsistencies of Dr. Tyndall’s article. 
1. Dr. Tyndall is astonished that the “blameless advent” of 
his “innocent” ‘*modest” “ unpretending ” volume should be 
looked upon as reiterating charges made against Forbes. An 
extract or two will settle this point. 
a. ‘‘ Had he (Rendu) added to his other endowments the 
practical skill of a land-surveyor, he would now be regarded as 
the prince of glacialists.” 
“* Professor Forbes, when he began his investigations, was 
acquainted with the labours of Rendu. In his earliest works 
upon the Alps he refers to those labours in terms of flattering 
recognition. But though as a matter of fact Rendu’s ideas were 
there to prompt him, it would be too much to say that he needed 
their inspiration.” 
Put these two passages into straightforward English, instead 
of Dr. Tyndall’s favourite style of insinuation, and they amount 
to this: that Forbes, having the accomplishments of a land- 
surveyor, and being acquainted with Rendu’s work, put this and 
that together and appropriated the discovery. 
6. Forbes had, in 1860, minutely informed Dr. Tyndall of 
the nature and amount of his knowledge of Rendu in 1842, It 
* Principal Forbes and his Biographers. 
¢ 
NATURE 381 
is not too much to say that Dr. Tyndall’s sentence quoted above 
is utterly inconsistent with the plain statement of Forbes, and 
so implies a serious personal charge against the latter. 
c. A similar serious charge is made, when Dr. Tyndall, know- 
ing that Forbes asserted that it was at his suggestion that Agassiz 
employed a theodolite or a fixed telescope, and that this had 
never been denied, carefully states that ‘‘the same instrument 
was employed the same year by the late Principal Forbes upon 
the Mer de Glace,” and that ‘‘ we are now on the point of seeing 
such instruments introduced almost simultaneously by M. Agassiz 
on the glacier of the Unteraar, and by Prof. Forbes on the Mer 
de Glace.” 
2. Dr. Tyndall tells us that his work was originally com- 
menced as a boy’s book, but that “the incidents of the past 
year”? (i.e. his controversy with Forbes) caused him to deviate 
from this intention, Have boys so altered since 1859 that such 
controversy has now become suitable for them when supplied in 
the ‘‘ International Series”? 
3. What I said with reference to the unpublished correspond- 
ence of Forbes was said without any special reference to Dr. 
Tyndall. It was simply my excuse to the reader for the very 
meagre use,I had made of so extensive and valuable a collec. 
tion. 
But, even in this matter Dr. Tyndall’s inconsistency is patent. 
He says that, longing for peace, he abstained from answering 
Forbes, not from inability to do so, but to avoid making Science 
the arena of personal controversy. Yet, in the same breath, he 
not only complains of my not publishing certain letters which he 
supposes to contain charges against himself, but (see §5 below) 
insinuates that I am acting from feelings of animosity ! ! 
4. Dr. Tyndall’s answer to one of Forbes’ charges is certainly 
to some extent plausible. I can say no more till I have an op- 
portunity of consulting Rendu, for it is quite obvious that it is 
possible by proper selection of portions of so vaguely-written a 
book to make him appear to say anything one chooses. 
Dr. Tyndall’s answer to the other charge is so obviously in- 
sufficient that I need not deal with it here. 
But more than this :—no ever-so-complete defence of himself 
on one or two points is any reply to the overwhelming pamphlet 
of Forbes, every line of which in its calm truthfulness calls for 
an answer. 
5. Dr. Tyndall refers to former controversy between us, and 
to its happy termination at a personal interview. Why Dr. 
Tyndall should bring before the public such matters as a private 
reconciliation, unless with the object of holding me up to scorn 
as the breaker of a solemn truce, 1 altogether fail to see. I need 
scarcely say that no one in his senses would enter into an agree- 
ment never in future to differ from another, nor to point out in 
his writings passages calculated to mislead. But the following, 
and other passages which I need not cite, are all so many half- 
mysterious insinuations (of the Tyndall kind) against me, and all 
tend towards the same implied accusations. 
‘* |. the fire was not extinct: the anger of former com- 
bats, which I thought spent, was still potential, and my little 
book was but the finger which pulled the trigger of an already 
loaded gun.” 
I shall be obliged by Dr. Tyndall’s pointing out to me a single ~ 
expression, in that part of Forbes’ Life which was wsitten by 
me, which is calculated to give him the slightest offence :—with 
the one exception of a letter from Forbes, which was specially 
written for publication; and which, for Forbes’ own sake, I 
would rather not have published. . 
No doubt he may be annoyed by my saying that little has 
since been added to the observations made by Forbes on glaciers. 
This is a matter of opinion. I do not think that Dr. Lyndall 
has made any addition of consequence to our knowledge of 
glaciers, and I am supported in this belief by many of the very 
highest authorities. But this is no charge against Dr. Tyndall. 
6. When I saw the ‘‘ Forms of Water, &c.,” I added a brief 
and excessively temperate statement to what I had already 
written, and I republished Forbes’ own defence of himself against 
Tyndall and Agassiz. Was I not bound to do something, and 
could I possibly have done less ? 
7. The rupture of the truce, or “‘ peace,” whatever that may 
be, was the work of Dr. Tyndall himself—partly by his ‘* Forms 
of Water, &c.” mainly by his article inthe Contemporary Review, 
So far as I am personally concerned, the public has no right to 
know my feelings :—but, whatever they are, they are mingled 
with the satisfaction I experience in being once more free, as of 
old, to point out to the public the misleading passages and actual 
