524 LETTER FROM COMMANDER W. E. COOKSOX, R.N. [Jlllie 20, 



margin of the plates of the carapace quite sharply defined as in 

 the young tortoises (which it resembled in shape), whereas in all 

 the full-grown tortoises we had hitherto seen these lines were almost 

 entirely gone. It was at this spot that our guide found, a few 

 months before our visit, the largest tortoise that he had seen for 

 the last fifteen years ; he estimated its weight at about 400 lb. 



"I have already mentioned that the shell of this large tortoise 

 was so decayed that I did not take it on board ; but I took some 

 measurements of it, and am satisfied from these and its shape that 

 the animal had the characteristics I have just described. The 

 epidermoid layer of the shell had for the most part come away ; but 

 where fragments were left, the marginal lines of the plates showed 

 quite distinctly. I suppose that abundance or variety of food 

 would be sufficient to produce this difference of appearance in the 

 tortoises from different localities in Albemarle Island, this part 

 of the island, the S.W. end, having a comparatively luxuriant vege- 

 tation, whereas the neighbourhood of Tagus Cove is described by 

 Mr. Darwin as being 'miserably sterile;' but it is a point not to 

 be overlooked that these two localities are separated by a coast-line 

 of 70 miles, and that between them lie three of the highest vol- 

 canic peaks of the whole group, one if not two of which have been 

 active until quite recently ; and from the flanks of all three streams 

 of black lava descend, each several miles in width. Again, the 

 most northern of these craters is situated almost in the centre of 

 the narrowest part of the island, just a little to the north of Perry 

 Isthmus, and sends down its black streams in all directions ; so that 

 this part of the island is exactly like Narborough Island opposite, 

 which is described as 'a great volcano, whose base is surrounded 

 by an extensive field of lava ; it is utterly barren and desolate.' I 

 think one may conclude that these lava streams are quite impass- 

 able to the tortoises, and that, as far as these creatures are con- 

 cerned, the north and south ends of the island are as effectually 

 separated as they would be by a channel of 40 or 50 miles of deep 

 water. 



"With regard to the greatly reduced numbers of these animals in 

 most of the islands, and probable extinction in others, it is known 

 that Charles and Chatham Islands have been inhabited for forty 

 years, which fully accounts for the extinction of the tortoises in 

 these islands, as they have always been eagerly sought for, the 

 oil made from their fat being very valuable and their flesh much 

 esteemed. Their habit of paying periodical visits to their water- 

 ing-places, and the very plain tracks which they make through 

 the bush or high grass, lead to their easy discovery. The 

 track of a large tortoise is exactly that which a cart with very 

 broad wheels and low body would make drawn over similar ground : 

 the feet make a trail such as the wheels would leave ; and between 

 the ' ruts ' the grass and low bushes are flattened down by the 

 animal as they would be by the body of the cart. Hood Island 

 never, I believe, had great numbers on it ; but James and Indefati- 

 gable Islands, where they were at one time so numerous and are 



