336 INTRUSIVE DIABASE IN TASMANIA. [May I9OO, 



How are these two conflicting accounts to be reconciled ? It 

 is unnecessary to point out that a report by so competent an ob- 

 server as Jukes, on a formation which he had personally examined, 

 could not be lightly set aside, and the explanation is not far to 

 seek. Between 1842 and 1845, H.M.S. Fly was engaged in 

 surveying the eastern coast of Australia and Tasmania, and Jukes 

 held the position of naturalist to the expedition. During the 

 progress of the survey, he appears to have made a trip from Hobart 

 to Port Arthur, at the southern extremity of Tasman's Peninsula, 

 where his ship was temporarily stationed. The only direct means 

 of conveyance at that time was the boat which carried mails, etc. 

 to the peninsula, and no deviation from its regular course would 

 be practicable. The first part of the route was by way of Ealph's 

 Bay to Frederick Henry Bay. The Neck would be crossed by means 

 of a tramway, which has long been disused, and the traveller 

 would pass the section which is the subject of this paper at a dis- 

 tance of about | mile, but he would have no opportunity of landing. 

 Jukes mentions several places which he personally visited, including 

 quarries from which fossils were obtained ; the nearest of these, 

 however, is distant about 18 miles from the Frederick-Henry Bay 

 section, and most of them are on tho other side of the Derwent 

 estuary. The paper appears to have been written three or four 

 years after the visit to Tasmania, and this might account for a 

 slight want of continuity and clearness in the reference to distinct 

 localities. The sketch, fig. 1, op. cit. p. 247 (there is no fig. i), 

 which immediately follows the account of the Frederick-Henry Bay 

 section, represents the cliff-section mentioned in the next two lines, 

 which is cited as a parallel instance. The latter is more fully 

 described in the second part of Jukes's paper, and was probably seen 

 by him from the deck of the Fly. 



PLATE XXII. 



Section showing the junction of diabase and altered sedimentary rocks in 

 Frederick Henry Bay (Tasmania). Reproduced from a photograph. 



