Jan. 14, 1SS6J 



NA 1 URE 



263 



Henry Cater Fulcher, and Harold Temple Wills, were elected 

 Fellows of the Society. — The following communications were 

 read : — Old sea-beaches at Teignmouth, Devon, by G. Wareing 

 Ormerod, F.G.S. The author stated that while old records 

 show that no important changes have taken place in the level 

 of the Teignmouth district during the historical period, the ex- 

 cavations made in recent drainage-operations in the present year 

 showed the existence of at least two series of beaches. The 

 oldest sea-beach, which is a few feet above the present sea-level, 

 was partly washed away and then covered up by later deposits 

 exhibiting evidence, in a number of delicate bivalve shells in an 

 unbroken condition, of having been deposited in a calm sea. — 

 On the gabbros, dolerites, and basalts of Tertiary age in Scotland 

 and Ireland, by Prof. John W. Judd, F.R. S. In previous 

 papers published in 1874 and 1876, it has been demonstrated 

 by the author that there exist in Scotland and in Hungary 

 igneous rock-masses presenting the most perfectly crystalline 

 characters, and belonging to the Tertiary period. It was further 

 shown that such highly crystalline, plutonic rocks are seen 

 passing in5ensibly into volcanic rocks of the same chemical 

 composition — gabbros into basalts, diorites and quartz-diorites 

 into andesites, and quartz-andesites and granites into rhyolites 

 — the lavas in turn graduating into the perfectly vitreous types 

 known as tachylites and obsidians. The present paper deals 

 with the basic rocks of Western Scotland and Northern Ireland, 

 which are shown to exliibit the most marked analogies with 

 rocks of the same age in the Faroe Isles and Iceland ; these 

 facts lend strong support to the doctrine of the existence of 

 petrographical provinces. The Tertiary age of the .Scotch and 

 Irish rocks is placed beyond dispute by the fact that they overlie 

 unconformably the youngest members of the Cretaceous system, 

 and are interbedded with stratified deposits of Lower Tertiary 

 age. With regard to the nomenclature of these rocks, the 

 identification of the more crystalline forms with the gabbros, 

 which was made by Zirkel and Von Las.aulx, is supported ; 

 while the use of the term "dolerite"as a convenient one for 

 the connecting links between the gabbros and basalts is advo- 

 cated. Of the original minerals contained in these rocks, 

 plagioclase felspar (ranging in composition from anorthite to 

 labradorite), augite, olivine, and magnetite, are regarded as the 

 e sential ones ; while enstatite, biotite, chromite, picotite, and 

 titanoferrite are among the most frequently occurring acces- 

 sories. It is shown, however, that these original minerals 

 may belong to different periods of consolidation. The Second- 

 ary minerals are very numerous, including quartz, epidote, 

 zoisite, hornblende, serpentine, and zeolites, with many other 

 crystallised and uncrystallised substances. There are remark- 

 able variations in the relative proportions of the original minerals 

 in different examples of the rock ; and by the complete dis- 

 appearance of one or other of the constituents, the gabbros are 

 sometimes found p.assing into picrites, eucrites, or troctolites. 

 In their microscopic structure these roclcs present many inter- 

 esting features. From the highly crystalline gabbros there are 

 two lines of descent to the vitreous tachylites : one through the 

 ophitic dolerites antl basalts, and the magma-basalts wtth 

 skeleton-crystals ; and the other through the gramiUtic dolerites 

 and basalts, and the magma-basalts with granular microliths. 

 The former are shown to result from the cooling down of molten 

 masses which were in a state of perfect internal equilibrium, 

 while the latter wej-e formed when the mass was subject to 

 movement and internal strain. It is shown that in the most 

 deeply-seated of these rocks (gabbros) the whole of the iron- 

 oxides combines with silica ; but, as we approach the surface, 

 the quantity of the.^e oxides separating as magnetite increases, 

 until it attains its maximum in the tachylites. In all the 

 varieties the order of separation of the different minerals is 

 shown not to depend solely on chemical causes, but to be influ- 

 enced by the conditions under which the rocks have cooled 

 down. Although these rocks are not highly-altered one-, yet 

 they afford admirable opportunities of studying the incipient 

 changes in their constituent minerals. The nature of these 

 changes is discussed, and they are referred to the following 

 causes : — (i) The corrosive action of the surrounding magma on 

 the crystals ; (2) the changes produced by solvents acting under 

 pressure in the deep-seated masses (these have been already 

 described under the name of " schilleris.ation ") ; (3) the action 

 of heated w.ater and gas escaping at the surface; (4) the action 

 of atmospheric .agents on the rocks when exposed by denuda- 

 tion ; and (5) the changes induced by pressure during the great 

 movements to which rock-masses are subjected. 



Physical Society, December 12, 1885. — Prof. Guthrie, 

 President, in the chair. — Mr. C. F. C.asella and Prof. T. E. 

 Thorpe were elected Members of the Society. — The following 

 papers were read : — On a magneto-electric phenomenon, by Mr. 

 G. H. Wyatt. The author had conducted a series of experi- 

 ments with a view of testing experimentally an expression ob- 

 tained by Mr. Boys for the throw of a copper disk suspended by 

 a torsion-tibre between the poles of an electro-magnet, when the 

 current was made or broken, and communicated by him to the 

 Society on June 28, 1884. Disks of various metals and of 

 various dimensions were used, the results being such as to agree 

 with the theory within narrow limits. It was, however, found 

 that when the throw of the disk was used to measure the mag- 

 netic field, the value obtained from the throw at break was uni- 

 formly greater than that obtained on making the current. Prof. 

 S. P. Thompson observed that the case presented was analogous 

 to that of the ballistic galvanometer, and that for the theory it 

 was necessary that the magnetic field should be made and 

 destroyed before the disk had moved sen-sibly. Mr. Boys 

 believed that the results of the experiments showed this to be 

 the case, since the result of such a movement would be to in- 

 crease the throw on breaking the current when the disk made 

 an angle of less than 45' with the lines of force, and to decrease 

 it when the angle was between 45° and 90°, whereas no such 

 variation from the theoretical result was observed. — On some 

 thermodynamical relations, by Prof. William Ramsay and Dr. 

 Sydney Young. In this paper experimental proof is given of 

 the following relations :—(i) The amount of heat required to 

 produce unit increase of volume in the passage from the liquid 

 to the gascDUs state, at the boiling-point under normal pressure, 

 is approximately constant for all bodies. (2) If these amounts 

 of heat be compared at different pressures, for any two bodies, 

 then the ratio of the amount at the boiling-poiiit under a 

 pressure, /j, to the amount at another pressure, /j, is approxi- 

 mately constant. (3) The products of the absolute temperature 

 into the rate of increase of pressure with rise of temperature are 

 approximately the same for all stable substances. (4) The rate 

 of increase of this product with rise of pressure is nearly the 

 same for all stable substances. (S) A relation exists between 

 the absolute temperatures of all bodies, solid or liquid, stable or 

 dissociable, which may be expressed in the case of any two 

 bodies by t he equation 



Ta and Tk bemg the absolute temperatures of the two bodies 

 corresponding to any vapour-pressure ; T'a and V b, absolute 

 temperatures at any other pressure ; and c, a constant which 

 may be zero or a small positive or negative quantity. (6) The 

 variations from constancy of the expression t'-P, though mall, 



maybe expies ed by a similar equation. (7) IfZ../, Z../, Lb, 

 and Lb, represent similar relations of latent heat at different 

 pressures, the same for A and B, it appears probable that 



^^ = ^ -I- c{rA- Ta). 



La' Lb' 

 (8) The ratio of the heats of vapori ation of any two bodies .at 

 the same pressure is approximately the same as that of their 

 absolute temperatures at that pressure. The authors conjecture 

 that this statement is also true of dissociating bodies. A large 

 part of the experimental work consisted in obtaining the relation 

 between vapour-pressure and temperature cf different substances, 

 values of — '^ had been obtained from these observations in two 



ways, by plotting curves with t and/ as co-ordinates and draw- 

 ing tangents, and by the method of differences. Prof. Perry 

 suggested that the curve should be expressed in such a form as 



log/ = «- J -r-' 

 which Rankine has shown to be a very true expression for 

 the relation between pressure and temperature, and that ^ 



shoidd be obtained from this by differentiation. Prof. Guthrie 

 hoped the authors would experiment upon the vapour-tensions 

 of mixed liquids, a subject to which he had himself given some 

 attention. 



Edindurgh 

 Royal Society, December 21, 1S85. — Prof. Douglas 

 Maclagan, Vice-President, in the chair.— Mr. J. V. Buchanan, 



c{T'^. 



Ta), 



