172 APPENDIX TO REPORT ON OYSTER CULTURE 



Description. — Blue, highly hydrated silty clay, intensely black in the 

 interior of the mass from the decomposition of organic matter, chiefly 

 derived from microscopic animal organisms, intermixed with sand of 

 local rocks, chiefly green and gray schists and grits, vein quartz, and 

 with broken shells. 



Mr. Hart describes the cleaned bottom of his pond as follows : — " It 

 has a basis of strong clay ; on this a dark shelly sand (left when the soft 

 mud [No. 13] was scraped off), and on the sand a thick coating of gravel, 

 which is now slightly coated with silt" [No. 13]. This silt covers the 

 bottom of the uncleaned portion of the pond, and " finds its way to the 

 cleaned part of the pond where the oysters are laid down, and appears to 

 have very nutritive properties." 



14. Lough Swilly. — Specimen of sand, gravel, <fcc, of the outer shore, 

 near Mr. Hart's pond. 



Description. — Sand and gravel : beach sand with intermingled pebbles 

 of various sizes, chiefly of schists, grits, vein quartz, melaphyre, a good- 

 sized pebble of limestone. Clay : Amber-coloured stiff clay, containing no 

 organic matter, and not flocculent like the deposited muds rich in micro- 

 scopical animal matter. 



Mr. Hart thus describes No. 14: — " Samples of the different sorts of 

 soil found in a spadeful of stuff dug from the open foreshore. In most 

 places the clay is further from the surface, the deposit of sandy mud and 

 gravel on it being deeper the greater is the distance from high water 

 mark. Shells, principally those of the Anomia or saddle oyster, are 

 plentifully scattered on the shore." 



The shores of Lough Swilly and the surrounding district consist of 

 gneiss, mica schist, quartz rock, and Lower Silurian altered limestone. 

 Greenstone dykes also occur in the slates. The soils, 11, 12, 13, and 

 14, are derived from these rocks. 



15. Ballysadare Bay, county of Sligo. — Three samples of mud from 

 one of the best beds belonging to Mr. Creighton. 



Description. — a. Beach sand composed of comminuted shells, quartz 

 sand, and brownish grits fragments. Bits of bright green sea-weed — 

 apparently an TJlva — were mixed up with the sand. 



b. Beach sand somewhat coarser than a, containing fragments of 

 chert, and small pebbles of grits. 



c. Sand of fine comminuted shells, worn fragments of shells, and 

 brownish grit pebbles. The latter and some of the shell fragments 

 were coated with patches of brownish red lichen-like sea- weed. 



There was very little clay-si] t in either of the specimens, which were 

 however small in quantity. Diatomacese and Rhizopoda could how- 

 ever be detected in it when separated as well as possible from the sand. 



16. Rosmuck, near Ballinahinch, county of Galway. — Sand from Mr. 

 Robinson's oyster grounds. 



Description. — White coral sand like that of Boundstone and other 

 bays on the coast of Galway, containing a few oyster shells and Lucina 

 Spinifera f?). The local rocks are granitoid and quartz rock, but the 

 coral sand contained no gravel or fragments of them. 



17. Sample of an oyster bed from the same district as No. 16. 

 Description. — A mass of oyster shells resting on coral sand intermixed 



with a fine dark grayish, very hydrated silt, rich in animal matter. No 

 trace of local gravel. 



18. Aughinish Bay, south shore of Galway Bay. — Sample of soil suit- 

 able for fattening oysters, said to be similar to the Red Bank of Burren. 



Description. — Fine porous calcareous sand, intermixed with a highly 

 hydrated silty clay, comminuted shells, and quartzose sand. There were 

 also many large fragments of univalve and bivalve shells, and fragments 



