Inyiocent : Ringed Plover, fi^r. , at Sheffield. 13 



of the formingf crystal, and thus become land-locked as it were. 

 Here, then, we have a hint that may serve to explain the 

 occurrence of quartz, flakes of mica, and prisms of plag"ioclase 

 as enclosures in the large crystals. 



The meshes of the growing- orthoclase crystals having 

 entangled and cut off", from the surrounding mass, small 

 portions of the magma, these would be robbed of their 

 orthoclase material to complete the building of their prison. 

 They could not recover equilibrium by diffusion, and we should 

 have a case of a rock forming within a rock ; for when the large 

 felspars were complete the little " land-locked" particles would, 

 under certain conditions, perhaps not until after intrusion had 

 taken place with the resulting further cooling, differentiate as 

 quartz, mica, and plagioclase. The still fluid magma, however, 

 would contain no free quartz or minerals other than those of 

 low solubility. From the regular distribution of the porphyritic 

 crystals in the consolidated rock it is rather suggested that the 

 mass must have been in a viscid condition, and at no very high 

 temperature, otherwise gravity would have acted and the large 

 crystals segregated. But this would only land us in another 

 difficulty, for if the mass was at a comparatively low temperature 

 when intruded how comes it that the surrounding rocks bear such 

 marked evidence, for a considerable distance, ot metamorphism ? 

 As this problem does not directly concern the life history of the 

 large felspars it would perhaps be better to leave it alone for the 

 present. 



BIRDS. 



Easington Bird Notes. — A Hoopoe was seen here on Oct. 

 17th, and on the 21st of November a male Bittern killed itself 

 by flying against the Lighthouse. In the last week in October 

 a few Little Stints were noticed, and a Little Auk on November 

 24th. — P. W. LoTEN, Easington, Dec. 4th, 1905. 



Ringed Plover, &c., at Sheffield. — Perhaps you may like 

 to record that Ringed Plover (generally accompanied by Dunlin) 

 visit the Redmires Reservoirs in this City every year on the 

 autumn migration, and the Golden Plover, Curlew, and Common 

 Sandpiper and Common Snipe breed close to the Reservoirs. Is 

 there another City in England with such a record ? — C. F 

 Innocent, Sheffield, Nov. 21st. 



1906 January i. 



