May 2°, 1873] 
an unknown cause” (‘* Occasional Papers,” p. 4), and worked 
out the subject thoroughly. 
In the Comptes Rendus for Oct. 18, 1841, a portion of a letter 
from Agassiz to Humboldt was published. Here he lays claim 
to the discovery without mentioning the name of Forbes. He 
speaks of it as ‘“‘le fait le plus nouveau que 7’ai remarqué.” 
Forbes felt deeply annoyed at this conduct of his friend, but 
contented himself with publishing his own discovery. A rupture 
between the two friends now commenced. About this time 
M. Guyot recollected that he had described this appearance in 
1838 to the Geological Society of France, at Porrentruy 
(“ Agassiz Etudes,” p. 207). Several people had seen the same 
thing previously. Among others, Sir David Brewster writes as 
follows :—‘‘ The Mer de Glace is like the waves of the sea, as 
if they had been fixed by sudden congelation ; when the ice is 
Most perfect, which is on the sides of the deep crevices, the 
colour is a fine blue. There is an appearance of a vertical 
stratification in the icy masses stretching in the direction of the 
valley in which the glacier lies. . . . The surface of the glacier 
exhibits also the appearance of veins exactly like blocks [?] of 
stone” (Yournal, 1814). In 1820, M. Zummstein saw it (‘‘ Bib- 
liothéque Universelle,” 1843). Col. Sabine and M. Elie de 
Beaumont had also seen it (‘‘ Travels in the Alps,” p. 29). 
But though seen it had not been studied, nor did any printed 
description of it exist. M. Guyot did not even print an abstract 
of his communication. It remained an isolated, unprinted, for- 
gotten fact until Forbes appeared upon the scene. Professor 
Tyndall has most justly said that neither Forbes nor Agassiz 
knew of it in 1841 (‘‘ Forms of Water,” p. 187). Yet though, 
as has just been proved, Forbes pointei it out to Agassiz in 
1841, the latter tried to show that he had known of Guyot’s 
observation (letter from Agassiz to Forbes, ‘* Life of Forbes,” 
Appendix B), and endeavoured to give the credit to Guyot rather 
than to Forbes (his own claims having been now disproved). 
If it be true that he knew what Guyot had done, then (1) why 
did he not mention it to Forbes and Heath, both of whom affirm 
(in contradiction to the statements of Agassiz) that Guyot’s 
Name was not mentioned? (2) Why did he not perceive the 
importance of the structure? (3) Why did he say that it was 
superficial? (4) Lastly, how could he reconcile it with his 
conscience to describe it to Humboldt as “‘le fait /e plus nou- 
veau que j'ai remarqué ?” 
The facts show (1) that Forbes was seriously wronged by the 
conduct of Agassiz; (2), that he discovered independently the 
veined structure ; (3) that he was the first to study the subject 
and give it its true place in reference to glacier theories. I have 
limited myself to the accusation contained in the letter of Mr. 
Alex, Agassiz. Whether he is correct in his appreciation of the 
estimate put upon Forbes’ labours, in Dr. Tyndall’s last popular 
work, I need not at present discuss. I know so well to what 
conclusion a comparison of that book with the writings of 
Forbes and other workers on glacier theories would lead, that I 
leave it confidently to the judgment of those “ fair-minded in- 
vestigators ” of whom Mr. Alex. Agassiz speaks. 
GEORGE FORBES 
P.S.—Mr. Heath’s testimony, to which I have referred, is 
given in the following extract from a letter dated Trinity Col- 
lege, Cambridge, Feb. 25, 1842 :—‘‘I will witness—tst, that 
he (Agassiz) knew nothing about it; 2nd, when he did see it he 
said it was superficial sand; 3rd, that he was the last to believe 
that it went to any depth. I think your account very true, and 
not claiming one jot more than fully belongs to you.” 
Cambridge, May 20 G. F. 
Perception and Instinct in the Lower Animals 
THE suggestion made by me in your issue of February 20, 
that animals which had been deprived of the use of their eyes 
during a journey might retrace their way by means of smell, had 
the effect of letting loose a flood of illustration, fact, and argu- 
ment bearing more or less directly on the question ; and as the 
stream now seems to have run nearly dry, I ask permission 
briefly to review the evidence adduced, so far as it affects the 
particular issue I brought forward. Several of the writers argue 
as if I had maintained that in all cases dogs, &c., find their way, 
wholly or mainly, by smell ; whereas I strictly limited it to the 
case in which their other senses could not be used. The cases 
of this kind adduced by your correspondents are but few. The 
first, and perhaps the most curious, is that of Mr. Darwin’s 
horse ; but, unfortunately, the whole of the facts are not known, 
NATURE 
65 
As Mr, Darwin himself pointed out, the horse may have lived in 
the Isle of Wight, and been accustomed to go home along that 
very road. I would suggest also that the country might resemble 
some tract in the neighbourhood of his own home; or that the 
horse, having been brought from home by a route and toa dis- 
tance of which it had no means of judging, thought its master 
was riding home on the occasion in question, and therefore ob- 
jected to turning back. Anyhow, the case is too imperfect to be 
of much value as evidence in so difficult a matter. ‘‘J. T.” 
(March 26) quotes the case of the hound sent ‘‘ from Newbridge, 
county Dublin, to Moynalty, county Meath,” thence long after- 
wards to Dublin, where it broke loose, and the same morning 
made its way back to its old kennel at Newbridge. I can find 
no ‘‘ Newbridge, county Dublin,” although there is a New- 
bridge, county Kildare, which is 26 miles from Dublin, on a 
pretty direct high road. That the dog never attempted to return 
during its ‘‘long stay” at Moynalty seems to show that some 
special facilities existed for the return from Newbridge. What 
they may have been we cannot guess at in the total absence of 
information as to the antecedents of the dog, the route by which 
he returned, and the manner in which he conducted himself on 
first escaping in Dublin, 
The next case, of the two dogs returning from Liverpool to 
near Derby, is vague, and also without necessary details. It 
happened 50 years ago, and the only evidence offered as to the 
mode of the dogs’ return is that “ it 7s said they were seen swim- 
ming the Mersey.” “N. Y.’s” case (April 24) of the dog who 
‘*did not make haste back,” and therefore could not have re- 
turned by smell, is also most inconclusive. The distance was 
only 20 miles, and we know nothing of the route the dog fol- 
lowed, or the time it took. How do we know the dog did not 
wait the three weeks till it saw someone it knew living at or 
near its former house, and followed that person? This appears 
to me to be an exceedingly probable way of accounting for 
many of these returns where the distance is not very great. This 
brings me to the case of Mr. Geo. R. Jebb, who seems to have 
gone to the trouble of making an experiment which, with a little 
more trouble, might have been very complete and satisfactory. 
The dog was taken by rail very circuitously from Chester to a 
place 10 miles from Chester. It ‘‘ hung about the station for 
about an hour and a half,” and in three hours more arrived at 
its home. But we are still left totally in the dark, both as to 
the route it took or the process by which it decided on that 
route. Whatis required in such experiments is, that a person 
not known to the dog should be ready to watch and follow it 
(on horseback), noting carefully on the spot its every action. We 
should then perhaps know why it ‘‘ hung about the station” an 
hour and a half before commencing its journey home, and after- 
wards, whether it showed any hesitation as to its route, and 
whether it followed the road or went straight across country. A 
few experiments carefully made in this way, at distances varying 
from 10 to 30 miles, and with a thorough knowledge in each 
case of the animal’s antecedents, would, I venture to say, throw 
more light on this interesting question than all the facts that 
have been yet recorded. The only experiment ofthis kind I have 
met with is in the work of Houzeau (‘‘ Etudes sur les Facultés 
Mentales des Animaux’’), and it is so curious that [ give the 
passage literally. He says (vol. i. p. 156): “I have succeeded 
in making young dogs of five or six months lose themselves on 
first going out with me. They would begin by seeking for my trace 
by smell ; but not succeeding in this, they would decide to return 
home. If there was a path, they followed the route by which 
they had come. If it was an untrodden virgin country, they 
shortened the circuits they had made in coming, but did not 
altogether depart from them. One would say that memory fur- 
nished a certain number of points which divided the route, and 
they went towards these by memory of directions. Thus in- 
scribing chords to the curve by which they had come, they re= 
turned to the house.” M. Houzeau’s general conclusion from a 
considerable body of observations made with this point in view 
is, that animals find their way by exactly the same means as man 
does under similar circumstances, that is, by the use of all their 
faculties in observation of locality, but especially by a memory 
of directions and by a ready recognition of places once visited, 
which serve as guide-posts when they are again met with. This 
seems to me a very sound theory, and quite in accordance with 
all that is known of the manner in which savages find their way, 
The more general objections to my little theory which are 
made in your leading article appear to depend on the denial, to 
such animals as dogs and horses, of that amount of common 
