i66 



NA TURE 



[December 15, 1892 



hand along the tube. Another series of experiments were per- 

 formed in varying magnetic fields. With a view to showing 

 Hertzian phenomena to large audiences the authors tried 

 Geissler tubes to replace the spark-gap in resonators, with great 

 success. When large Leyden jar circuits were used the effects 

 were very brilliant. Another form of resonator consisted of a 

 bent wire terminating in two plates, between which an exhausted 

 tube was placed. This tube became luminous when the 

 resonator was placed in the vicinity of a fairly large Hertz 

 oscillator. Other experiments similar to those shown before the 

 society at Cambridge by Prof. J. Thomson, on discharges in 

 exhausted bulbs were then made, the bulbs being placed with a 

 coil of wire of four turns, forming the connection between the 

 outer coatings of two small jars, whilst sparks passed between 

 knobs connected with the inner coatings. The bulbs glowed 

 brightly at each discharge, rings of light being seen near their inner 

 surfaces. On putting a ring tube outside the coil this was also 

 seen to glow. The most brilliant part of the glow always 

 occurred in close proximity to the wire coil. A secondary coil, 

 wound by the side of the above-mentioned primary, could be 

 short-circuited at will ; this had the effect of decreasing or 

 extinguishing the luminosity in the bulb or tube. Bright sparks 

 passed between the secondary terminals when held a short dis- 

 tance apart, but the shock experienced by touching the ends was 

 not serious. The above arrangement, with the addition of two 

 Geissler tubes placed in series between the outer coatings of the 

 jars, was used to illustrate the fact that closing the secondary 

 diminishes the impedance of the primary circuit of a transformer. 

 Experiments on condensers made of tin-foil on glass were shown. 

 In one of them, parts of the coatings in the form of letters had 

 been removed, and the spaces became luminous when the con- 

 denser was connected with an induction coil. In another 

 experiment a glass plate was moved to and from a condenser, 

 and a musical note could be heard whose pitch increased as the 

 distance between the glass plates diminished. The note was 

 said to be the octave of an open organ pipe, whose length was 

 equal to the distance between the plates. Mr. Swinburne thought 

 some of the effects shown were not Hertzian, but merely cases of 

 ordinary mutual induction. He inquired whether the vacuum 

 tubes would still glow if the Leyden jars were removed from the 

 so-called resonating circuits. He was also of opinion that in 

 the magnetic experiments the surfaces of the bulbs, and not the 

 enclosed gases, took the charges. Mr. Watson asked if the 

 authors had tried screening off the long waves by a wet cloth. 

 If the effects still existed, this would prove that they were 

 Hertzian. Mr. Blakesley wished to know if the images of the 

 rotating tubes were at equal angular distances. Mr. Smith 

 pointed out that these distances were not equal, but corresponded 

 to equal changes of poteniinl. Prof. Ayrton remarked that the 

 only cases where the materials of the bulbs, tubes, &c., did not 

 influence the results were those in which discharges were pro- 

 duced by varying magnetic fields. Mr. E. T. Carter thought an 

 induction coil a more efficient machine for producing the glow 

 in tubes than the alternator, &c., used by Mr. Tesla, Mr. 

 Trotter asked if the authors had observed whether the glow 

 produced by passing a discharge through a wire wound in a long 

 pitch spiral round a tube formed an open or a closed circuit of 

 light. Prof. S. P. Thompson said he first noticed that sparks 

 passed between pieces of metal in the vicinity of an induction 

 coil sparking into a condenser in 1876, when he was showing 

 some experiments on telegraphic apparatus before the society, 

 but unfortunately he did not pursue the subject. Long before 

 Mr. Tesla's investigations Dr. Bottomley had shown that 

 exhausted tubes could be caused to glow, but it was not until 

 Tesla produced such phenomena on a large scale that people 

 recognized how much light could be got in that way. Mr. 

 Rimington, in replyintf to a question by Prof, Thompson, said 

 the notes heard when the glass plate approached the con- 

 denser were of very high pitch. The explanation why in the 

 experiments performed in varying magnetic fields, the bright 

 parts of the luminous discharges were near the wire, appeared 

 to be that the E. M.F. was greatest in these places. Although 

 he had not tried the experiment, suggested by Mr. Swinburne, 

 of taking off the Leyden jar, he felt sure that doing so would 

 stop the glow. 



Geological Society, November 23.— W. H. Hudleston, 

 F.R. S,, President, in the chair. — The following communica- 

 tions were read : — Outline of the geological features of Arabia 

 Petrspa and Palestine, by Prof. Edward Hull, F.R.S, The 

 region may be considered as physically divisible into five sec- 

 NO. 1207, VOL. 47] 



tions, viz. (i) The mountainous part of the Sinaitic Peninsula; 

 (2) the table-land of Badiet-el-7ih and Central Palestine; (3) 

 the Jordan- Arabah valley ; (4) the table-land of Edoni, Moab, 

 and the volcanic disliict of Jaulan and Hauran ; and (5) the 

 maritime plain bordering the Mediterranean. The most ancient 

 rocks (of Archsean age) are found in the southern portion of 

 the region ; they consist of gneissose and schistose masses pene- 

 trated by numerous intrusive igneous rocks. They are suc- 

 ceeded by the lower carboniferous beds of the Sinaitic peninsula 

 and Moabite table-land, consisting of bluish limestone with 

 fossils, which have their counterparts chiefly in the carboniferous 

 limestone of Belgium, and of a purple and reddish sandstone 

 (called by the author " the desert sandstone," to distinguish it 

 from the Nubian sandstone of Cretaceous age), lying below 

 the limestone. The Nubian sandstone, separated from the 

 carboniferous by an enormous hiatus in the succession of the 

 formations, is probably of Neocomian or Cenomanian age, and 

 is succeeded by white and grey marls, and limestones with flint, 

 with fossils of Turonian and Senonian ages. The Middle 

 Eocene (Nummulitic limestone) beds appear to follow on those 

 of Cretaceous age without a discordance ; but there is a real 

 hiatus, notwithstanding the apparent conformity, as shown by 

 the complete change ot fauna. In Philisiia a calcareous sand- 

 stone in which no fossils havi been observed is referred to the 

 Upper Eocene ; for the Miocene period was a continental one, 

 when faulting and flexuring was taking place, and the main 

 physical features were developed— «.^. the formation of the 

 Jordan-Arabah depression is referable to this period. In Plio- 

 cene times a general depression of land took place to about 

 200-300 feet below the present sea-level, and littoral deposits 

 were formed on the coasts and in the valleys. To this period 

 belong the higher terraces of the Jordan-Arabah valley. The 

 Pliocene deposits consist of shelly gravels. Later terraces were 

 formed at the epoch of the glaciation of the Lebanon moun- 

 tains, when the rainfall was exce>sive in Palestine and Arabia, 

 The volcanoes of the Jaulan, Hauran, and Arabian desert are 

 considered to have been in active operation during the Miocene, 

 Pliocene, and Pluvial periods ; but the date of their final ex- 

 tinction has not been satisfactorily determined. After the read- 

 ing of this paper the president remarked on the interest of the 

 geology of an area, which was that of the Bible. Many 

 authors had recorded their observations on this district, one of 

 the latest being the author of this paper. Some years ago Mr. 

 Holland had read a paper before the Society, and he (the 

 speaker) believed that that writer was actually the first to prove 

 the existence of carboniferous fossils in the Sinaitic pe;. insula. 

 He remarked that Lcpidodendron mosaicum, described by 

 Salter, was somewhere preserved in the Society's museum, so 

 that the Society had long ago had evidence of carboniferous 

 rocks. Mr. Bauerman's paper, which was a reconnaissance in 

 a comparatively unknown district, created great interest ; and 

 when that paper was read doubt was expressed as to whether 

 the fossils then exhibited were carboniferous or triassic. After 

 the researches of Prof. Hull there was no doubt that carbon- 

 iferous rocks do occur in the region. As regards the granitic 

 rocks (extending far up the Nile valley, in the Sinaitic penin- 

 sula, and elsewhere), they were all of much the same character, 

 and, according to Sir William Dawson, occurred at two horizons 

 — the lower rocks being granitoid and gneissic, the upper more 

 or less volcanic, but still pre-carboniferous. He asked the 

 author whether the Poudingues de Jebel Haroun of Lartetwere 

 or were not ancient volcanic rocks. The Nubian sandstone of 

 older writers included many things, but the a^e of the various 

 sandstones was now satisfactorily determined by the author. 

 Some were carboniferous, others (in the speaker's opinion) ceno- 

 manian. The calcareous formations of Judasa were well known 

 from the writings of Lartet, Fraas, and others ; but the exact 

 line of demarcation between the Nummulitic limestone and the 

 true Cretaceous had never been determined. It was a curious 

 fact, as staled by Von Zittel, that not one fossil was common 

 to the two deposits, which were nevertheless quite conformable. 

 Miocene beds appeared to be absent, for, as noted by Lartet 

 and confirmed by the author, this was a period of movement, 

 when the great valley and the great fault were initiated. He 

 (the speaker) felt that there were many difficulties connected 

 with the depression which had not yet been cleared up. Lartet, 

 Hitchcock, and others had traced the general direction of the 

 fault ; but the author had determined its exact site at more than 

 one point. The most interesting point in this connection was 

 the question of the age of the 700-foot sad lie separating the 

 Akabah watershed from the Jordan-Arabah depression. This 



