MEETINGS. 13 



Jethou, the arrangements for the excursion being left to the 

 Secretary. 



Monthly Meeting held July 8th, 1890, Mr. J. Whitehead, 



Vice-President, in the chair. 



The minutes of the last meeting having been read and 

 confirmed, Captain Percy Groves, Mr. H. L. Humphreys, and 

 Mr. J. Jenkins were elected members of the Society, and 

 Miss Gilbert, Miss Turner, Miss Heppel and Miss Beaty were 

 proposed for election at the next meeting. 



Mr. Derrick then read a lively, chatty description of the 

 Excursion to Jethou on June 25th, to which was appended 

 the list of Lepidoptera and Coleoptera, found by Mr. Luff on 

 that occasion. Mr. Marquand followed with a paper on " The 

 Flora of Jethou." Mr. Marquand succeeded in identifying 

 during the few hours he was on Jethou no less than 133 

 flowering plants and ferns, among them one species found 

 in one spot only in England, and one in the north-west of 

 France. This was exhibited by Mr. Marquand, as were also 

 the moths, butterflies, beetles and bees captured by Mr. Luff. 



Mr. Collenette, F.C.S., next read a note on " The Geology 

 of Jethou," exhibiting specimens of the rocks in illustration of 

 his subject. 



The island of Jethou is practically an immense outcrop of a 

 single rock. The appearances and weathering differ but little in the 

 various visible portions, and the eye is at once caught by the general 

 squareness of the detached and semi-detached blocks. In most cases 

 the section is but slightly removed from a perfect square, the lines 

 formed by the angles running along for several feet almost parallel. 



The enormous size of the blocks is worthy of remark. One 

 block quite detached, and by no means the largest, which measured 

 roughly 12 feet square and 10 feet long, would weigh nearly 120 

 tons. Some of the immense blocks on the west side would be three 

 times that weight. 



Present appearances give an idea that Jethou was originally 

 more than twice its present height, aud possessed very steep sides. 

 Owing to this very little soil has been retained, and the rock masses 

 are pretty freely visible in situ all over the island. 



The rocks at the summit show but small differences, but on the 

 sea shore especially towards the north-east there is more variety. 



The general character of the rock is, I believe, a quartz-syenite, 

 that is, the chief minerals are felspar, quartz and hornblende. I have 

 not traced any mica hence. I do not name it a granite, though the 

 appearance in situ gives the impression that it is one. 



The first specimen I submit, I look upon as typical of the mass 

 of the rock (No. 1). I obtained it from a portion of the cliff which 



