July 30. 1853.] 



NOTES AND QUERIES. 



109 



English and Frencli charts from that found in the 

 galleon taken by Commodore Anson, and of which 

 a copy is given in the account of his voyage. 

 Cook, or Lieutenant Roberts, the compiler of the 

 charts to his third voyage, retained them ', and 

 La Porouse was the first to erase them from the 

 map. There can, indeed, be little doubt of their 

 identity with the Sandwich Islands. But although 

 Cook was not actually the first European who had 

 visited those islands, to him rightly belongs all the 

 glory of their discoveiy. Forgotten by the Spa- 

 niards, misplaced on the chart a thousand miles 

 too far to the eastward, and unapproached for 

 240 years, their existence utterly unknown and 

 unsuspected, Cook was, to all intents and pur- 

 poses, their real discoverer. C. E. Bagot. 

 Dublin. 



of a stranger. But " N. & Q." must not be made a 

 channel for erroneous statements, and we "natives 

 and to the manner born" must be allowed to know 

 best what is in our own museums. 



W. PiNKERTON. 

 Ham. 



MEGATHERIUM AMBRICANUM. 



(Yol. vii., p. 590.) 



Is not the cast of a skeleton in the British Mu- 

 seum, recently alluded to by A Foreign Surgeon, 

 and which is labelled Megatherium Americanum 

 Blume., better known to English naturalists by its 

 more correct designation of Mylodon rohustus 

 Owen ; and if so, why is the proper appellation 

 not painted on the label ? If that had been done, 

 A Foreign Surgeon would not have fallen into 

 the ei-ror of confounding the remains of two dis- 

 tinctly different animals. 



Might I beg leave to add, for the information of 

 your correspondent, that no British naturalist " of 

 any mark or likelihood," has ever assumed that 

 (though imdoubtedly sloths) either the Mylodon, 

 Scelidotherium, or Megatherium, were climbers. 

 Indeed, the whole osseous structure of those 

 animals proves that they were formed to uprend 

 the trees that gave them sustenance. By no other 

 hypothesis can we intelligibly account for the im- 

 mense expanse of pelvis, the great bulk of hind- 

 legs, the solid tail, the massive anterior limbs 

 furnished with such powerful claws, and the ex- 

 traordinary large spinal chord — all these the 

 characteristic features of the Mylodon, 



Whether there were palms or not at the period 

 of the tellui'ic formation, I cannot undertake to 

 say ; but as A Foreign Surgeon assumes that a 

 palm is an exogenous tree (!), I am induced to 

 suspect that his acquaintance with geology may be 

 equally as limited as his knowledge of botany. 

 Besides, what can he mean by speaking of a sloth 

 " the size of a large bear ? " Why, the Mylodon 

 must have been larger than a rhinoceros or hippo- 

 potamus. The veriest tyro in natural history 

 would see that at the first glance of the massive 

 skeleton. 



It is a painful and ungracious task to have to 

 pen these observations, especially, too, in the case 



PHOTOGRAPHIC CORRESPONDENCE. 



Ste7'eoscopic Angles. — Like many of your cor- 

 respondents, I iiave been an inquirer on the sub- 

 ject of stereoscopic angles, which seems to be still 

 a problem for solution. What is this problem ? 

 for until that be known, we cannot hope for a 

 solution. I would ask, is it this? — Stereoscopic 

 pictures should create in the mind precisely such a 

 conception as the two eyes would if vicioing the ob- 

 ject represented by the stereograph. If this be the 

 problem (and I cannot conceive otherwise), its 

 solution is simple enough, as it consists in placing 

 the cameras invariably 2^ inches apart, on a line 

 parallel to the building, or a plane passing through 

 such a figure as a statue, &c. In this mode of 

 treatment we should have two pictures possessing 

 like stereosity with tliose on the retinas, and con- 

 sequently with like result ; and as our eyes enable 

 us to conceive perfectly of any solid figure, so 

 would the stereograph. I believe, therefore, that 

 this is, under every circumstance, the coi'rect 

 treatment ; simply because every other mode may 

 be proved to be false to nature. 



Professor Wheatstone recommends 1 in 25 when 

 objects are more than 50 feet distant, and this 

 rule seems to be pretty generally followed. Its 

 incorrectness admits of easy demonstration. Sup- 

 pose a wall 300 feet in extent, with abutments, 

 each two feet in front, and projecting two feet 

 from the wall, at intervals of five feet. The 

 proper distance from the observer ought to be 

 450 feet, which, agreeably with this rule, would 

 require a space of 18 feet between the cameras. 

 Under this treatment the result would be, that 

 both of the sides, as well as the fronts, of the three 

 central abutments would be seen ; whilst of all 

 the rest, only the front and one side would be 

 visible. This would be outraging nature, and 

 false, and therefore should, I believe, be rejected. 

 The eyes of an observer situated midway between 

 the cameras, could not possibly perceive either of 

 the sides of the buttress opposite to him, and only 

 the side next to him of the rest. This seems to 

 me conclusive. 



Again, your correspondent <£>. ("Vol. vii., 

 p. 16.) says, that for portraits he finds 1 in 10 a 

 good rule. Let the sitter hold, straight from the 

 front, i. e. in the centre, a box 2^ inches in width. 

 The result would be, that in the stereographs the 

 box would have both its sides represented, and 

 the front, instead of being horizontal, consisting 

 of two inclined lines, i, e. unless the cameras were 



