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BRITISH ASSOCIATION FOK THE ADVANCEMENT OF SCIENCE. 



[1854. 



heating effect had been observed as far back as 1838. Since January 

 last Mr. Gassiot has had several forms of apparatus constructed for 

 the purpose of observing the phenomena of secondary discharge in 

 relation to its heating effects : — 1. If the discharge of the secondary 

 current takes place in air the negative terminal (which in these experi- 

 ments were of platina wire) became heated. — 2. If the wires are sealed 

 into small (thermometer) straight tubing neither terminal appears to 

 be heated, but the discharge takes place, filling the entire tube with a 

 brilliant clear white light. — 3. If any piirt of the tube is blown into 

 small bulbs that portion of the discharge which passes througli the 

 bulbs is spread as illuminating that portion with a lirilliant blue light. 

 — 4. If the discharge takes place in a globe, or in a tube of about one 

 inch diameter, the negative terminal is intensely heated. In the course 

 of the experiments Jlr. Gassiot noticed that the glass at the heated 

 end became quite black ; in fact, the heat of the electrode had fused 

 the glass and reduced the lead. He, therefore, had another apparatus 

 constructed, taking care that whenever he experimented with it the 

 current should invariably be sent in the same direction. The result 

 has been that the negative end has become quite black, the glass being 

 apparently oxidized in regular layers, the most intense being nearest 

 the wire. The positive end of the glass remains quite clean, as does 

 the platina wire, except about 1-92 of an inch, wliich appears covered 

 with a minute black deposit. At this terminal, whenever the discharge 

 is made, a minute, but brilliant spark appears, from which the electric 

 brush flows in great beauty and brilliancy. The negative is at first 

 covered with the well known blue flames until it becomes red hot, or 

 no deposit appears to remain in the negative te-minal. In all the 

 experiments made with closed glass tubes the air was exhausted by 

 means of an air pump. 



The sudden disappearance of stars beliind the moon, without any 

 cliange or diminution of their brilliancy, was one of the most beautiful 

 phenomena that could be witnessed. 



On the Structure of Lunar Volcanic Craters : hij Mb. James Nasmtth. 



This communication was illustrated by a model of the lunar volcano 

 Copernicus, and a diagram of Simpelius ; each of which consists of a 

 plateau, with a small central cone, surrounded by a ring shaped eleva- 

 tion, exhibiting concentric ridges or terraces. The circular elevations 

 were supposed to have been formed by the accumulation of materials 

 erupted with great energy to various distances, according to the inten- 

 sity of the force; giving rise to concentric ridges, or terraces of deposi- 

 tion, which are often nearly entire circles, one within the other. Besides 

 these there are other terraces, forming only segments of circles within 

 the principal rings, which were attributed to the agency of landslips, 

 these in most instances correspond to notches in the edge of the crater 

 from which they have slipped, and their debris has rolled onward over 

 the plateau, towards the centre. The central cone was attributed to 

 the last expiring efforts of the eruptive action. 



Prof. Phillips observed that although there might be no sign of the 

 existence of water on the present surface of the moon, he thought 

 there were many indications of former aqueous action. There were 

 elevations like the escars of Sweden and Ireland, and small gullies 

 converging into larger, like the channels of mountain streams. He 

 also called attention to the narrow, dark lines, many miles in length, 

 occasioned by shadows which change with the direction of the sunlight, 

 showing that the level is higher on one side than the other, as in cases 

 oi fault. Mr. Hopkins inquired into the evidence respecting the exist- 

 ence of an atmosphere, or of water, on the moon. If any atmosphere 

 existed, it must be very rare in comparison with the terrestrial atmos- 

 phere, and inappreciable to the kind of observations by which it had 

 been tested ; yet the absence of any refraction of the light of stars 

 during occulation was a very refined test. No equal means existed of 

 ascertaining the presence of water on the moon; and if it did not now 

 exist, the opinion of its former existence rested on very uncertain 

 evidence. The large size of the lunar craters compared with any on 

 the earth was accounted for if they were produced by the expansion of 

 a fluid mass ; for there was no reason why such a force should be 

 materially less in the moon than the earth, whilst gravitation was 

 much less. The result would be not only a much greater elevation, 

 but less tendency to fall. He considered the annular craters were the 

 remains of dome-shaped elevations, of which the central part had fallen 

 in. The lunar craters were more numerous in proportion to the ter- 

 restrial; but there might have been many more on the earth which 

 have been washed away. Mr. James Smith remarked that the perfec- 

 tion of the lunar volcanoes might be due to atmospheric conditions ; 

 and referred to the great circular crater of the Sandwich Islands as 

 being terraced like Copernicus. Mr. Nasmyth expressed his very 

 strong conviction of the total absence of water, or of traces of watery 

 action, on the moon ; and also of the absence of any atmospherci 



On the Probable Former Existence of PalcEozoic Glaciers: by Peop. 

 Bamsat. 



Admitting the probability that the earth had cooled down from a 

 molten condition, the author contended that little trace of that refri- 

 geration could be detected, as regards the climate of the globe, since 

 the formation of the oldest fossiliferous strata. For a long time it had 

 been supposed that the coal Flora indicated the influence of high 

 internal temperature ; the same inference was derived from the 

 reptiles of the oolites and the nautili of the tertiaries. It had however 

 lately been shown that the Silurian Fauna indicated a temperate 

 climate in our latitude, and the other instances might be accounted for 

 by a different geography. He then proceeded to show what he con- 

 sidered evidence of glacial action, during the Latest PaliBOzoic period, 

 in South Staffordshire and the Malvern district. This consisted in the 

 occurrence of trappean breccia, sometimes more than 100 feet thick, 

 amidst the marls and sandstones of the Permian series, or resting on 

 the Silurian strata of Malvern and the Abberleys, where it had been 

 described as trap by Sir R. Murchison. The base of the breccia is a 

 fine soft red marl, lilce tertiary boulder-clay, containing angular masses 

 of trap, of various sizes, up to two or three feet in diameter, seldom 

 much water-worn, but having their surfaces more or less flattened and 

 polished and scratched like stones from the moraines of Alpine glaciers. 

 These blocks consist of greenstone, feldspars and feldspathic porphy- 

 ries, altered slate-rocks, ribboned slates, green slates and sandstones, 

 purple slates, and quartz rock, not derived from the underlying rocks, 

 but brought from the Longmynd and Silurian Strata north of Bishop's 

 Castle, some of them having travelled more than forty miles. The 

 Longmynd is now only 1,900 feet above the sea; but on its eastern 

 side, between it and the breccias, there is the great Church Stetton 

 fault, a downthrow to the west of 3,500 feet. And although an eleva- 

 tion of even 6,000 feet would not give rise to glaciers on the Longmynd, 

 Prof. Ramsay believed that in the Permian period they formed a moun- 

 tain tract from which glaciers descended to the sea, and bergs broke 

 off and floated away, as in the latest glacial seas. There are traces of 

 this action being renewed twice, — the last being in the new Red Sand- 

 stone. Outlying fragments of Upper Silurian rest on the Longmynd, 

 showing that it was originally covered, whilst the breccias prove that 

 its denudation took place before the Permian period. 



Sir C. Lyell admitted the failure of the old proofs that internal heat 

 had controlled the climate within the historico-geologic period. The 

 idea of glaciers in the Permian age was rather startling, and out of 

 harmony with the fact that large Monitors existed in Thuringia, and 

 tree-ferns flom-ished at the same period; but it was quite possible that 

 the Permian period included temperate and torrid climates, just as 

 both were found indicated in the tertiary. Prof. Phillips stated, that 

 when he first examined this trappoid breccia at Malvern, where it 

 exists at an elevation of 1,000 feet, he had been impressed with the 

 conviction that it was very different, as to its origin, from the ordinary 

 conglomerates of the new Red Sandstone, and even the notion of a 

 glacial explanation had passed though his mind. Mr. Page declared 

 himself a believer in the operation of glacial action from a period much 

 earlier than the Permian ; some of the conglomerates of the Old Bed 

 Siindstone were so like the accumulations of angular detritus carried 

 by bergs and piled up on the shores of Polar Seas, that an Arctic 

 voyager might suppose them formed in the same manner. Prof. Morris 

 referred to the existence of a series of fossils, apparently indicating a 

 warm climate in the strata immediately beneath the supposed glacial 

 deposit, and to the recurrence of a similar series in the beds immedi- 

 ately above ; and also to the existence of rock-salt and gypsum, sup- 

 posed indications of a warm sea, in the New Red Sandstone. Prof. 

 Forbes observed, that if the views of Prof Ramsay were confirmed, 

 they would throw great light on the changes of organic life at the close 

 of the Permian period. 



On the Thickness of the Ice of the Ancient Glaciers of Korth Wales, and 



other Points bearing on the Glaciation of the Country : by 



Pkof. Ramsay. 



Prof. Ramsay stated his belief that there had been two sets of glaciers 



in North Wales since the ground assumed its present general form. 



The first was on a very large scale, followed by a slow subsidence of 



the whole country to the extent of 2,300 feet, until only the tops of 



