May 17, 1888] 



NA TURE 



61 



Survey. The maps, on the scale of 6 inches to a mile, 

 show the remarkable geological structure of the west of 

 Sutherland. A series of enormous dislocations runs in a 

 southerly direction from the mouth of Loch Eriboll to 

 Skye. By these disruptions the most ancient rocks 

 have been torn up from great depths, and have 

 been launched bodily westwards, sometimes for several 

 miles. The displaced masses now rest upon other shifted 

 portions or upon wholly undisturbed rocks, and the ex- 

 traordinary structure is presented of vertical and highly 

 inclined strata, with their unconformable junctions stand- 

 ing upon gently inclined and much younger rocks. The 

 diagrams are taken across some of the more typical parts 

 of the district, and give some idea of the physical prob- 

 lems presented by this region, which undoubtedly ex- 

 hibits the most complicated geological structure in the 

 British Isles. 



Sections and specimens illustrating the recent borings 

 in the Delta of the Nile, exhibited by Prof. J. W. Judd, 

 F.R.S., on behalf of the Delta Committee. The whole of 

 the samples obtained in these borings have now reached 

 the Royal Society, and the examination of the materials 

 reveals some facts of great geological interest. The 

 alterations and mixtures of blown sand and Nile alluvium 

 were found to continue down to the depth of 121 feet from 

 the surface and 95 feet below the level of the Mediter- 

 ranean. At that depth a remarkable change in the 

 deposits took place, and beds of gravel containing both 

 pebbles and subangular fragments of quartzite, chert, 

 compact limestone, with some metamorphic and igneous 

 rocks, were found ; and similar beds occur at intervals 

 down to the greatest depth reached. Up to the present 

 time no contemporaneous organic remains have been 

 found in these deposits. 



Fossil plants from Ardtun in Mull, exhibited by Mr. J. 

 Starkie Gardner. These plants are from a small patch of 

 limestone beneath the gravels and silts of an old river 

 course sealed up in the great trap flows of Western 

 Scotland. The limestone is rather below the leaf-bed 

 found at Ardtun by the Duke of Argyll, and directly 

 overhangs the sea, the cliffs beneath being columnar and 

 worn into caverns. The plants were until recently 

 believed to be Miocene, but are now recognized to be 

 very low down in the Eocene— vide recent writings of 

 Sir W. Dawson and the Marquis de Saporta. The same 

 plants ranged over Greenland and North America during 

 the Tertiary, perhaps not synchronously, and an allied 

 flora seems to exist at the present day in China and 

 Japan. 



Photographs illustrating experiments in mountain- 

 building, exhibited by Mr. Henry M. Cadell, H.M. 

 Geological Survey of Scotland. These have already 

 been referred to in Nature. 



Set of thermometers specially constructed by Casella 

 for use by Mr. Symons in determining the present tem- 

 perature of the mineral springs in the Pyrenees, exhibited 

 by Mr. G. J. Symons, F.R.S. ; and Immisch's avitreous 

 thermometer, constructed for the above investigation. This 

 thermometer is absolutely perfect, its verification at Kew, 

 before and after its use in the Pyrenees, being o c- o at all 

 points from 50 to 130 . 



An apparatus for determining the hardness of metals or 

 other substances, exhibited by Mr. Thomas Turner. 



Robertson's writing telegraph, exhibited by Mr. John 

 M. Richards. 



A Coulomb-meter, exhibited by Prof. George Forbes, 

 F.R.S. This consists essentially of a conductor of iron wire 

 in the form of a spiral, or a double ring with cross wires. 

 Above the conductor a set of vanes is pivoted. This con- 

 sists of a circular disk of mica with a hole in the centre in 

 which' is fixed a paper cone carrying at its apex a pinion 

 with a concentric ruby cup. Round the circumference of 

 the mica disk eight small cylinders of pith are fixed at 

 equal distances, and eight vanes inclined at 45° to the mica 



disk are attached to the pith cylinders, these vanes being 

 made of the thinnest mica. This set of vanes is supported 

 by the ruby cup resting on a steel point fixed to the base 

 of the instrument. The pinion engages with the first wheel 

 of a train of wheelwork actuating the indexes, which show 

 upon dials the number of revolutions made by the vanes. 

 The action of the instrument is very simple. The electric 

 current passing through the iron conductor creates heat, 

 which sets up a convection current in the air, and this 

 causes the vanes to rotate about the vertical axis and 

 drive the clockwork. The number of revolutions indicated 

 on the dials is, through a considerable range of currents, 

 an exact indication of the number of coulombs or 

 ampere-hours which have passedth rough the conductor. 

 The friction of the ruby cup on the pivot determines 

 the smallest current which can be accurately measured, 

 and the friction of the clockwork is barely perceptible. 

 The resistance of a meter to read from 1 ampere upwards 

 is o - 02 ohm. 



Electrical translucent balloon for flashing signals by 

 night, invented and exhibited by Mr. Eric Stuart Bruce. 



The new iridio-platinum incandescent gas-burner 

 (Lewis and Sellon's patents), exhibited by Messrs. 

 Johnson, Matthey, and Co. 



Apparatus for measuring the changes produced by 

 magnetization in the dimensions of rods and rings of iron 

 and other metals, exhibited by Mr. Shelford Bidwell, 

 F.R.S. The instrument exhibited is capable of measur- 

 ing changes of length to a millionth of a millimetre 

 or a twenty-five-millionth of an inch. An iron rod when 

 magnetized becomes (as is well known) at first slightly 

 lengthened. But if the magnetizing force is sufficiently 

 increased it again contracts, and ultimately becomes 

 actually shorter than when unmagnetized. A cobalt rod 

 contracts under magnetization, reaching a minimum 

 length in a field of about 500 C.G.S. units, beyond which 

 point it becomes longer. A nickel rod also contracts ; the 

 limit of its contraction not having been reached with the 

 greatest magnetizing forces yet used. Bismuth is slightly 

 elongated in intense fields. (See Proc. Roy. Soc, vol. xliii., 

 1888, p. 406.) 



Experiments illustrating low-temperature spectra, irt 

 connection with the spectra of meteorites, shown by 

 Mr. J. Norman Lockyer, F.R.S. 



Skeleton of an Akka, a Negro tribe from Central 

 Africa, the smallest known race of men. (Height exactly 

 4 feet.) Sent by Dr. Emin Pasha for the British Museum, 

 and exhibited by Prof. Flower, C.B., F.R.S. 



Charts showing lines of equal values of the magnetic 

 elements (epoch 1880) — declination or variation, inclina- 

 tion or dip, horizontal force (British units), vertical force 

 (British units) — exhibited by Staff-Commander E. W. 

 Creak, R.N., F.R.S. From the original charts at the 

 Admiralty, compiled by Staff-Commander E. W. Creak, 

 and prepared in their present form for the " Report on 

 the Magnetical Results obtained in H.M.S. Challenger," 

 in the concluding volume of the "Voyage of H.M.S. 

 Challenger." The small maps show— (1) The track of 

 H.M.S. Challenger where magnetic observations were 

 made. (2) The approximate distribution of the secular 

 change in the declination or variation (epoch 1840-80). 



Photographs of the polar axis of a 5-foot telescope, 

 December 1887, January 1888, exhibited by Mr. A. A. 

 Common, F.R.S. 



Sir William Thomson's models of foam or froth con- 

 sisting of equal bubbles, exhibited by Prof. G. H. Darwin, 

 F.R.S. Each bubble is a curvilinear fourteen-faced space. 

 If a single bubble be dissected from the mass, it is found 

 to be derived from the regular octahedron (two square 

 pyramids base to base) by truncating the six solid angles. 

 Thus the eight faces of the octahedron give rise to eight 

 curvilinear hexagons, and the six solid angles to six solid 

 curvilinear squares. In the foam three films meet at 120 

 at each edge, and of the three which meet two are hexa- 



