Mar. :6, 1888,] 



SCIENTIFIC NEAVS. 



259 



rectangular horizontal components, which were written 

 in ink on a long band of paper, which under ordinary 

 circumstances is being slowly led forward by means of 

 clockwork. On the occurrence of an earthquake the 

 paper feed is automatically greatly increased, and again 

 after a few minutes slowed to its ordinary rate ; the auto- 

 matic apparatus being adjusted by the clockwork itself, 

 so as to be ready for another earthquake. Any number 

 of successive earthquakes could thus be recorded on the 

 same ribbon without trouble to the investigator. Time 

 is marked by means of an accurate timepiece on the 

 paper ribbon every five minutes, and a distinguishing 

 mark is made every hour. Mr. A. W. Meikle read a 

 paper " On the Measurement of Electric Currents by 

 the Electrolytic Deposition of Copper." Dr. James 

 Colville, M.A., submitted the following motion : — "That 

 a philological section of the Philosophical Society be 

 formed, and that a committee, to be afterwards nomi- 

 nated, be appointed to draft a constitution for the 

 section." 



GEOLOGICAL SOCIETY OF LONDON. 

 At the meeting held on February 29th, W. D. 

 Blanford, LL.D., F.R.S., President, in the chair, the 

 following communications were read : — - 



I. "An Estimate of Post-Glacial Time." By T. Mel- 

 lard Reade, Esq., C.E., F.G.S. 



The author showed that there exists on the coasts of 

 Lancashire and Cheshire an important series of Post- 

 Glacial deposits which he has studied for many years. 

 The whole country to which his notes refer was formerly 

 covered with a mantle of low-level marine Boulder-cla3" 

 and sands, and the vallej's of the Dee, Mersej', and Ribble 

 were at one time filled with these glacial deposits. 



These glacial beds have been much denuded, especiallj' 

 in the valleys, where the rivers have cleared them out, 

 in some cases, to the bed rock. Most of this denudation 

 occurred during a period of elevation succeeding the de- 

 position of the low-level Boulder-clay. On this eroded 

 surface and in the eroded channels lie a series of Post- 

 glacial beds of a most interesting and extensive nature. 

 They consist of estuarine silt and Scrobicit/aria-clay 

 covered by extensive peat-deposits, containing the stoois 

 of trees rooted into them. Upon these lie, in some 

 places, recent tidal silts, and on the coast margin blown 

 sand and sand dunes. The series of events represented 

 by the denudation of the Low-level Boulder-clay and 

 the laying down of these deposits is as follows : — ist, 

 elevation succeeding the Glacial period, during which time 

 the Boulder-clay was deeply denuded in the valleys. 

 2nd, subsidence to about the 2S-feet contour, when the 

 estuarine silts and clays were laid down. 3rd, re-ele- 

 vation, representing most probably a continental con- 

 nection with the British Isles, during which time the 

 climate was milder than at present, and big trees 

 flourished where now they will not grow. 4th, sub- 

 sidence to the present level, the submersion of the peat 

 and forest-beds, the laying down of tidal silt upon them, 

 and the accumulation of blown sand along the sea- 

 margin, extending to a considerable distance in an inland 

 direction. 



It was estimated, from a variety of considerations, 

 that these events, all posterior to the Glacial period, 

 represent a lapse of time of not less than 57,500 years, 

 allotted as follows: — 40,000 years for the elevation suc- 

 ceeding the Glacial period measured by the denudation 



of the Boulder-clay in the valleys, 15,000 years for the 

 accumulation of the estuarine silts, clays, peat, and forest 

 beds, and 2,500 years for the blown sand. 



2. " Note on the Movement of Scree-Material." By 

 Charles Davison, Esq., M.A. Communicated by Prof. 

 T. G. Bonney, D.Sc, LL.D., F.R.S., F.G.S. 



The author noticed the frequent high angle of slope of 

 screes, and called attention to Canon Moseley's observa- 

 tions on the downward creep of lead on the roof of 

 Bristol Cathedral, and his subsequent experiment, and 

 stated his belief that stones free to move on the surface 

 of a scree must be affected in the same manner. This 

 he proved by experiments, the result of which he 

 described. 



These experiments showed that stones do move down- 

 wards, owing to alternate contraction and expansion, the 

 movements accompanying or occurring a short time after 

 the change of temperature, that the descent is greatest on 

 days of bright sunshine, interrupted frequently by pass- 

 ing clouds, and that rain slightly increases the rate of 

 descent. 



A description was given of a scree on Hindsrarth, 

 Cumberland, in which the stones lie with their longer 

 axes pointing down the slope; and it was pointed out 

 that the movement of the stones in the way described 

 would cause the surface-stones to fall off those on which 

 they rested, and that others would be dislodged during 

 their descent. A numerical estimate was then made of 

 the total amount of movement produced on a scree of a 

 certain size by expansion and contraction of the surface- 

 stones, and after alluding to the relative efficiency of this 

 and other agents iipon various screes, the author con- 

 cluded by pointing out that in the case of the moon 

 this might be almost the only agent at work. 



3. " On some Additional Occurrences of Tachylyte." 

 By Grenville A. J. Cole, Esq., F.G.S. 



An intrusive sheet, some 8 feet thick, among the 

 basalts of Ardtun Head in Mull, has selvages of tachylyte. 

 The specific gravity of the glass is 2-83, and in other 

 respects it resembles the examples already described 

 from the west of Scotland. 



An analysis of the Ardtun spherulitic tachylyte shows it 

 to resemble that of Beal in Skyp, having 53 per cent, of 

 silica and nearly 6 per cent, of alkalies. 



An occurrence of tachylyte at Kilmelfort, Argyll, was 

 noted, and a description given of an example of great 

 beauty from the Quiraing in Skye. The latter rock shows, 

 in section, a fight-brown translucent glass, with abun- 

 dant cumulites and small brown spherulites with radial 

 structures. 



Near Bryansford, County Down, in Ireland, a basalt 

 dyke occurs, the selvage of which must have originally 

 resembled the tachylyte of the Quiraing. 



In conclusion, the well-known variolite ofthe Durance 

 was cited as a rock of basic character, comparable, in its 

 perlitic and spherulitic structures with the acid " pyro- 

 merides," both types having alike suffered from secondary 

 devitrification. 



4. "Appendix to Mr. A. T. Metcalfe's paper 'On 

 Further Discoveries of Vertebrate Remains in the 

 Triassic Strata of the South Coast of Devonshire, be- 

 tween Budleigh Salterton and Sidmouth.'" By H. J. 

 Carter, Esq., F.R.S. Communicated by A. T. Metcalfe, 

 Esq., F.G.S. 



A microscopic examination of certain calcareous pellet- 

 like bodies, containing plates possessing a bony structure, 

 and referred to in Mr, Metcalfe's paper in the Society's 



