332 Obituary — Prof. P. Martin Duncan. 



A VAEIETY OF PICRITE (SCTELITE) IN SARK. 

 Sir, — Eatber more than two years since (Dec. Ill, Vol. VI. p. 109) 

 I wrote a description of a variety of Picrite which I had found in 

 boulders at Port du Moulin, Sark, stating that I published it, as 

 there was " no probability of my returning to Sark for years, if 

 ever," in the hope some one would trace this interesting rock to its 

 home. But the unexpected often happens : last summer's work 

 among the hornblende schists of the Lizard determined Mr. Hill 

 and myself to re-examine those of Sark, and in the process of this 

 the picrite was not forgotten. After a careful search along the 

 rocks at low water we found a dyke of this rock at the foot of the 

 cliffs between Port du Moulin and Saignie Bay, nearly opposite to 

 (perhaps rather to the south of) the Grand Autelet. It is at the base 

 of a little spur from the cliff of banded gneiss, into which it is 

 intrusive, but it only shows for a foot or so above the shingle, in two 

 or three humps, running seawards. In this direction, about fifteen 

 yards off among the boulders, is another boss. I have examined the 

 rock under the microscope. The olivine is not so well preserved, 

 there is rather less mica and more hornblende than in the specimen 

 described in 1889 ; it is not quite so obviously connected with the 

 serpentines, but I have no doubt that the boulder came from some 

 part of this dyke. We searched the cliffs very carefully up to the 

 further side of Saignie Bay on the north, and for some distance to the 

 south of Port du Moulin without finding any other dyke. We 

 now think it very improbable that Ansted, in speaking of a dyke 

 of serpentine as crossing the island, referred to this rock. We 

 reserve further particulars for a paper in which we hope to com- 

 municate to the Geological Society the result of our work in Sark. 



T. G. BONNEY. 



PETER MARTIN DUNCAN, 



M.B. (LOND.), F.R.S., F.G.S., F.L.S,, ETC. 

 Born, 20th April, 1824. Died, 28th May, 1891. 

 Peter Martin Duncan was born at Twickenham in 1824, and 

 received most of his early education in the Grammar School there. 

 After leaving this he lived for a short time in a school in Switzerland, 

 and on his return to England entered the Medical Department of 

 King's College, in September, 1842. He there received the whole 

 of his formal scientific training; he passed the preliminary M.B. 

 examination with honours in Anatomy and Physiology in 1844, and 

 obtained the full degree in 1846 ; he was elected an Associate of 

 his College in 1849. Upon the conclusion of his medical studies, 

 he acted for a time as assistant to a doctor at Eochester, whence he 

 removed to Colchester, where a practice had been purchased for him. 

 Here he remained for many years, and it was during this period that 

 he published his first scientific essay, which consisted of " Observations 

 on the Pollen tube, its growth, histology and physiology" (1856). 

 But he did not at Colchester secure much time for original research, 

 for most of that which was left him by his profession was occupied 



