MARINE BIOLOGICAL STATION AT PORT ERIN. 31 



masses, cementing together the dead shells and sand grains 

 which are lying on the bottom and making lumps like 

 "clinkers." Hence the spot where it is found is called 

 by the trawlers the " Blacksmith's Shop." It is about 25 

 miles S.S.W. of the Calf of Man (see PI. I), in ordinary 

 clear weather the Chicken Kock lighthouse just dipping 

 and the Stack at Holyhead just rising above the water, 

 and the depth is about 25 fathoms. We first heard of 

 this interesting material from Mr. W. Beck, of Douglas, 

 and he kindly sent a specimen to Mr. A. Leicester at Port 

 Erin. Mr. Leicester found the following shells in the con- 

 cretion : — Pecten opercularis, Gyprina islandica, Venus 

 lincta, Cardium echinatum, Nucula nucleus, Scrobicularia 

 alba, Lucina borealis, and Turritella terebra. We have 

 obtained other specimens since, there is a fine lump in 

 the Biological Station at Port Erin, and we have pre- 

 sented another piece to the Jermyn Street Museum in 

 London. Mr. W. W. Watts, of the Geological survey, 

 has made a careful examination by thin sections of the 

 latter specimen, and he has kindly sent me the following 

 notes in regard to it : — " The microscopic examination 

 shows that it is practically a fine grained grit made up of 

 the usual constituents of fragmental rocks cemented 

 together, the cement being in greater quantity that the 

 grains. 



"These grains are chiefly chips of quartz, but I have 

 also seen microcline, orthoclase felspar, plagioclase felspar, 

 brown mica, a few grains of glauconite, and green and 

 brown pseudomorphs, probably after grains of some ferro- 

 magnesian mineral like augite, hornblende or even possibly 

 olivine — which, it is impossible now to say, but I think 

 most probably hornblende. There are one or two quite 

 opaque grains and several clear grains containing a good 

 deal of minute magnetite. The grains vary in size within 



