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NATURE 



{May 17, 1888 



The first Harkness Scholarship for Geology and Palaeontology 

 is to be awarded in June next ; names of candidates are to be 

 sent in by May 31 next. Candidates must be Bachelors of Arts 

 of not more than two-and-a-half years' standing. 



The Sheepshanks Astronomical Exhibition will be awarded 

 next December, at Trinity College. It is open to all under- 

 graduates of the University, but the person elected must become 

 a member of Trinity College. The conditions may be learnt 

 from Dr. Glaisher, Trinity College. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, April 26. — " On the Development of the 

 Electric Organ of Raia bads." By J. C. Ewart, M.D., Regius 

 Professor of Natural History, University of Edinburgh. Com- 

 municated by J. Burdon Sanderson, F. R.S. 



The paper consists of a short description of the electric organs 

 found in the skate genus, and of an account of the development 

 of the electric organ of the common grey skate {Raia batis). 



It is shown that while in some skates {e.g., Raia batis) the 

 organ is made up of disk-shaped bodies, in others {e.g., Raia 

 fullonica) it consists of numerous cup-shaped structures provided 

 with long or short stems. 



The disks (with the development of which the paper chiefly 

 deals) consist essentially of three layers, viz. (1) an electric plate 

 in front in which the nerves end ; (2) a striated layer which 

 supports the electric plate ; and (3) an alveolar layer, posterior 

 to which is a thick cushion of gelatinous tissue. Each disk is 

 formed in connection with a muscular fibre. In] young embryos 

 there is no indication of an electric organ, but in an embryo 6 or 

 7 cm. in length, some of the muscular fibres at each side of the 

 notochord are found in process of conversion into long slender 

 clubs having their heads nearest the root of the tail. 



The club-stage having been reached, the muscular fibre next 

 assumes the form of a mace, and, later, the anterior end further 

 expands to form a relatively large disk, while the remainder of 

 the original fibie persists as a slender ribbon-shaped appendage. 

 As the head of the club enlarges to form a disk, it passes 

 through an indistinct cup-stage, which somewhat resembles the 

 cups of the adult Raia fullonica, hence it may be inferred that 

 in Raia fullonica the organ has been arrested in its develop- 

 ment. The conversion of the muscular fibre into a club is 

 largely caused by the increase, at its anterior end, of muscle- 

 corpuscles. These corpuscles eventually arrange themselves, 

 either in front of the head of the club, to give rise to the elec- 

 tric plate, or they migrate backwards to form at the junction of 

 the head of the club with its stem the alveolar layer. The 

 striated layer, which is from the first devoid of nuclei, seems to 

 be derived from the anterior striated portion of the club. 



The gelatinous tissue between the disks, and the connective 

 tissue investing them, are derived from the embryonic connective 

 tissue corpuscles, which exist in great numbers around the clubs 

 and developing disks. 



May 3. — "On the Relations of the Diurnal Barometric Maxima 

 to certain Critical Conditions of Temperature, Cloud, and 

 Rainfall." By Henry F. Blanford, F.R.S. 



The author refers to an observation of Lamont's that the 

 diurnal barometric variation appears to be compounded of two 

 distinct elements, viz. a wave of diurnal period, which is very 

 variable in different places, and which appears to depend on the 

 horizontal and vertical movements of the atmosphere and 

 changes in the distribution of its mass, and a semi-diurnal 

 element which is remarkably constant and seems to depend 

 more immediately on the action of the sun. Then, referring to 

 the theory of the semi-diurnal variation, originally put forward 

 by Espy, and subsequently by Davies and Kreil, the author 

 points out that the morning maximum of pressure approximately 

 coincides with the instant when the temperature is rising most 

 rapidly. This is almost exactly true at Prague, Yarkand, both 

 in winter and summer, and in winter months at Melbourne. At 

 the tropical stations, Bombay, Calcutta, and Batavia, and at 

 Melbourne in the summer, the barometric maximum follows the 

 instant of most rapid heating by a shorter or longer interval ; 

 and the author remarks that this may probably be attributed to 

 the action of convection, which must accelerate the time of 

 most rapid heating near the ground surface ;. while the baro- 

 metric effect, if real, must be determined by the condition of 



the atmosphere up to a great height. With reference to 

 Lamont's demonstration of the failure of Espy's theory, a con- 

 dition is pointed out which alters the data of the problem, viz. 

 the resistance that must be offered to the passage of the pres- 

 sure-wave through the extremely cold and highly attenuated 

 atmospheric strata, whose existence is proved by the phenomena 

 of luminous meteors. 



With respect to the evening maximum of pressure, it is pointed 

 out that very generally, and especially in India, and also at 

 Melbourne, there is a strongly-marked minimum in the diurnal 

 variation of cloud between sunset and midnight, which, on an 

 average, as at Allahabad and Melbourne, coincides with the 

 evening maximum of the barometer. A similar coincident 

 minimum, even more strongly marked, characterizes the diurnal 

 variation of the rainfall at Calcutta and Batavia in their respect- 

 ive rainy seasons. In the author's opinion these facts seem to 

 point to a compression and dynamic heating of the cloud- 

 forming strata, and he points to the existence of a small irregu- 

 larity in the diurnal temperature curves of Prague, Calcutta, and 

 Batavia, which may possibly be due to such action. It is further 

 remarked that the evening maximum about coincides with the 

 time when the evening fall of temperature, after a rapid reduction 

 between 6 or 7 and 10 p.m., becomes nearly uniform in rate, 

 and it is suggested that the former may possibly be determined 

 by the check of the rate of collapse of the cooling atmosphere. 

 But it is observed that both the morning and evening waves of 

 pressure probably involve other elements than the forced waves, 

 and are in part rhythmic repetitions of previous waves. 



Geological Society, April 25.— W. T. Blanford, F.R.S., 

 President, in the chair. — The following communications were 

 read : — Report on the recent work of the Geological Survey in 

 the North- West Highlands of Scotland, based on the field-notes 

 and maps of Messrs. Peach, Home, Gunn, Clough, Hinxman, 

 and Cadell. Communicated by Dr. A. Geikie. At the outset 

 a review was given of the researches of other observers, in so 

 far as they forestalled the conclusions to which the Geological 

 Survey had been led. Reference was made to the observations 

 of Macculloch, Hay Cunningham, C. W. Peach, and Salter; 

 to the prolonged controversy between Sir Roderick Murchison 

 and Prof. Nicol ; to the contributions of Hicks, Bonney, 

 Hudleston, Callaway, Lapworth, Teall, and others. It was 

 shown that Nicol was undoubtedly right in maintaining that 

 there was no conformable sequence from the fossiliferous quartzites 

 an.l limestones into the eastern schists. It was also pointed out 

 that the conclusions of Prof. Lapworth regarding the nature and 

 origin of the eastern schists involve an important departure from 

 Nicol's position, and are practically identical with those obtained 

 independently by the Geological Survey. The results of the 

 recent survey work among the Archaean rocks may be thus 

 summarized : (1) the eruption of a series of igneous rocks of a 

 basic type in which pegmatites were formed ; (2) the develop- 

 ment of rude foliation in these masses, probably by mechanical 

 movement, and their arrangement in gentle anticlines and syn- 

 clines, the axes of which generally run N.E. and S.W. ; (3) 

 the injection of igneous materials, mainly in the form of dykes, 

 into the original gneisses, composed of {a) basalt rocks, {b) peri- 

 dotites and palseopicrites, {c) microcline-mica rocks, ((/) granites ; 

 (4) the occurrence of mechanical movements giving rise to dis- 

 ruption-lines trending N.W. and S.E., E. and W., N.E. and 

 S.W. ; (5) the effects of these movements on the dykes were to 

 change the basalt-rocks into diorites and hornblende-schists, the 

 peridotites and palseopicrites into talcose schists, the microcline- 

 mica rocks into mica schists, and the granites into granitoid 

 gneiss ; (6) the effects on the gneiss resulted in the formation of 

 sharp folds trending generally N.W. and S.E., the partial or 

 complete reconstruction of the original gneiss along the old 

 foliation-planes, and finally the development of newer schist- 

 osity more or less parallel with the prominent disruption-lines. 

 There is an overwhelming amount of evidence to prove that all 

 these various changes had been superinduced in the Archaean 

 rocks in pre-Cambrian time. After reviewing the facts bearing 

 on the denudation of the Archaean land-surface, the order of 

 succession and thickness of the Cambrian strata were given, from 

 which it is apparent that the deposits gradually increase in thick- 

 ness as we pass southwards from Durness to Loch Broom. 

 Prior to the deposition of the Silurian sediments the Cambrian 

 strata were folded and extensively denuded. By these means 

 various Cambrian outliers were formed far to the east of the 

 present limits of the formation. The order of succession of the 

 Silurian strata along the line of complicated structure from 



