ON THE CONVEBSION OF SEDIMENTARY MATERIALS. 239 



extent ? Has it diminished during the last ten years ? 7. Is the ordinar}' water-level 

 ever affected by local rains, and, if so, in how short a time ? And how does it stand 

 in regard to the level of the water in the neighbouring streams, or sea ? 8. Analysis 

 of the water, if any. Does the water possess any marked jjecidiarity ? 9. Section 

 with nature of the rock passed through, including cover of Drift, if any, with thioh- 

 itess ? 9«. In which of the above rocks were springs of water intercepted ? lO. 

 Does the cover of Drift over the rock contain surface springs ? 11. If so, are these 

 land springs kept entirely out of the well ? 12. Are any large faults known to 

 exist close to the well ? 13. Were any Irine springs passed through in making 

 the well? 14. Are there any salt springs in the neighbourhood? 15. Have any 

 wells or borings been discontinued in your neighbourhood in consequence of the 

 water being more or less brackish ? If so, please give section in reply to query No. 

 9. 16. Kindly give any further information you can. 



Re'port of the Committee, consisting of Dr. H. C. Sorby, Professor 

 W. Eamsay, and Professor W. J. Sollas, appointed for the pur- 

 pose of investigating the Conditions under which ordinary Sedi- 

 mentary Materials may he converted into Metamorphic Rocks. 

 Drawn up by Professor W. J. Sollas {8ecretary\ 



The Committee have entered upon this investigation by commencing a 

 .study of the effect of highly-elevated temperatures and pressures on the 

 solubility of minerals and chemical compounds ordinarily insoluble in water. 



They have succeeded in obtaining a simply constructed tube, in which 

 the experimental substances can be heated in the presence of water to a 

 high degree of temperature (300-400° C.) without the escape of steam. 

 The tube consists of cast iron, is 4 in. long, with an internal diameter of 

 5 in., and walls | in. thick ; the mouth is closed by a conical iron stopper 

 ground to fit, and secured by screws and nuts to a marginal flange ; to 

 ensure complete tightness a washer of copper, or other soft refractory 

 metal, is introduced before screwing up. 



Silica is the first substance which has been selected for examination, 

 and the experiments with it have only recently been taken in hand. They 

 have been conducted by Mr. Hunter, under the supervision of Professor 

 Ramsay, in the laboratory of University College, Bristol. 



(1) A fragment of colourless, transparent quartz was reduced to fine 

 powder, placed in a cage of platinum wire gauze, and so introduced into 

 the tube, along with 10 cubic centimetres of water. The tube was then 

 closed, and heated by a Bunsen's burner to a temperature of 300° C. for 

 two days. There was no sign of action ; no residue was left on evapora- 

 tion of the water, and the surface of the quartz retained its lustre. 



(2) Some powdered chalcedony taken from a clear hyaline specimen 

 was similarly treated. It was slightly attacked, and on evaporation a 

 distinct residue was left. 



(3) Some chemically pure silica was next prepared by precipitation 

 from sodium silicate with hydrochloric acid, evaporation to dryness, 

 thorough washing, and subsequent ignition. After ignition it was placed 

 in the experimental tube, and heated to 300° C. for two days. At the 

 conclusion of the experiment the impalpable powder of silica was found 

 to have caked together into a white opaque granular mass. On examina- 



