May ii, 1882J 



NA TURE 



45 



familiar. Kdnig's method of introducing a small tube commu- 

 nicating; with a manometric capsule and a flame indicator, was 

 recently described in our Physical Notes. The latest device for 

 a similar purpose is that of M. Serra-Carpi, who introduces a 

 small microphone supported on an elastic membrane stretched 

 over a wire ring. The microphone is connected by wires to a 

 telephone and a battery. Hardly any sound is heard except 

 when the exploring microphone is at a node, when it causes a 

 buzzing sound to be heard in the telephone. The objection to 

 all the^e methods is that the pressure of the explorer alters the 

 position of the nodes in the tube. Konig's apparatus is probably 

 least open to this objection, but it requires a special piece of 

 apparatus of an expensive kind. 



THE JOINTING OF ROCKS AND THE 

 CHANNEL TUNNEL^ 



THE writer, referring in the first instance to his " Report" on 

 ■*■ Jointing, published in vol. xxv. (1S75) of the Transactions 

 of the Royal Irish Academy, in which the subject is treated of in 

 its purely geological aspect,-' remarks that his investigations in 

 connection with it entitle him to take a part in the discussion of 

 a question in engineering, which public enterprise has of late 

 elevated to one of international importance. 



At the outset, however, he feels himself compelled to express 

 his doubts that rock-jointing has been sufficiently attended to by 

 the active promoters of the proposed Channel Tunnel. 



The remarkable divisional structure under consideration, often 

 taken to be analogous to ordinary cracks or fractures due to 

 rock-disruption, is, in the opinion of Prof. King, a phenomenon 

 having only a distant relation in its origin to the latter. 



In its normal state, jointing is a fis-ured condition of rocks — 

 the fissures presenting even, smooth, regular, and close-fitting 

 conjunctive planes, often standing vertically, or in an inclined 

 position. Where the fissures have been affected by stratic dis- 

 turbances, or have been acted on by water and other erosive 

 agencies, they are more or less open, thereby converted into 

 " crevices." It divides both sedimentary beds and igneous 

 masses ; and is separable into two or more series or systems, 

 each having its respective fissures running in parallelism, also 

 in a definite and an independent direction, over areas hundreds 

 of miles in extent ; and descending to considerable depths below 

 the earth's surface. The fissures vary in their distance from one 

 another from under half an inch to two or more feet. 



That jointing demands the closest attention on the part of 

 engineers engaged in sub-aqueous works requires no other proof 

 than the fact of the utter failure which attended the scheme for 

 opening out, during the famine of 1845-48, a water communica- 

 tion, about four miles in length, between Lough Corrib and 

 Lough Mask, in the west of Ireland. After an expenditure of 

 40,000/. it was found that the jointing in the carboniferous lime- 

 stone, through which the excavation had been made, carried off 

 all the water. The work had, therefore, to be abandoned ; thus 

 resulting in nothing more than a dry ditch ! 



As regards the chalk and other rocks to be penetrated for the 

 Channel Tunnel, Prof. King admits that they may not be so 

 highly jointed as the much older carboniferous limestone ; never- 

 theless, he shows that the former deposits are not altogether free 

 from dangers, which, to be overcome, require the closest 

 attention. 



From the numerous occurrences, noticed by writers, and ob- 

 served by himself, of faults, true jointing, 3 ordinary disruptive 

 fractures, inclined bedding openings, dry submarine swallow- 

 holes of Pliocene age (now filled with clay, sand, gravel, in some 

 cases containing sub-fossil sea-shells) and rock porosity in the 

 chalk formations of Kent, Prof. King infers that these detriments 

 are equally present in the same deposits, well known to exist at 

 the bottom of the Channel ; where some of them cannot but turn 



1 Abstract of a paper " On the Jointing of Rocks, in Relation to Engi- 

 neering, especially the Tunnelling of the Strait of Dover," by William King, 

 D.Sc, Professor of Mineralogy ard Geology, Queen's College, Galway, 

 read April 24 at the Royal Irish Academy. Dublin. 



2 Jointing in its relation to Physical Geography has been lately treated 

 of by the author in "Thalassa and Xera in the Permian Period," appended 

 to the work — An Old Chapter of the Geological Record, &c, by Professors 

 King and Rowney. 



3 The " many small faults" and " very marked and constant joints "— 

 the latter sometimes containing infiltrated flint— which characterise the chalk 

 •'cliffs in many places near Margate" (Whitaker) must be familiar to 

 numbers of the citizens of the metropolis. " Numerous vertical crevices," 

 doubtless originally jointing, intersect a bed of chalk fifty feet thick, close to 

 Dover, at the base of Shakespeare's Cliff. — (\V. Phillips.) 



out to be sources of water-leakage, greatly interfering with the 

 success of the proposed Channel Tunnel. 



Precisely similar detriments, giving rise to the same apprehen- 

 sions are to be met with on the opposite seaboard of France. 

 Reference may be made to the great lines of fracture which have 

 moulded the river-drainage system of the Has Boulonnais ; and 

 especially to the marvellous jointing (represented by the distin- 

 guished geologist, M. Daubre'e, in his " Etudes Synthetiques de 

 Geologie," parte prem.), which vertically intersects the chalk 

 cliffs near T report, north of Dieppe. 



Still, such serious drawbacks Prof. King admits must not be 

 held as unsurmountable. He is fully satisfied that engineering 

 in the present day is quite able to cope with them ; but only by 

 an enormous expenditure. It has been proposed to line the 

 Tunnel with concrete ; bat in his opinion it is absolutely neces- 

 sary that nothing short of lining it, and in its entire length, with 

 the most resisting, impervious, and endurable stone, should be 

 attempted. 



UNIVERSITY AND EDUCA TIONAL 

 INTELLIGENCE 



Cambridge. — The accommodation recently provided for 

 practical biological work has already proved seriously deficient, 

 owing to the rapid growth of the classes in physiology and 

 comparative morphology. The class-room for practical mor- 

 phology was built to accommodate thirty students working at 

 the same time, and the room for histology, 36. Additional 

 temporary accommodation has been made for an increased num- 

 ber of students, but there are grave inconveniences in conse- 

 quence. This year there are about fifty-five students in elemen- 

 tary morphology, and twenty in the advanced class ; seventy 

 students attend elementary physiology, and about fifteen the 

 advanced course. The only possible alternative to the provision 

 of new rooms, is the division of classes into sections, and 

 repeating the practical work with each section ; rendering a 

 large increase in teaching power necessary. Moreover, such an 

 arrangement will interfere with the rule that the practical work 

 belonging to the lecture is gone through immediately after. 

 Under these circumstances it is recommended by the Museums 

 and Lecture Rooms Syndicate that a third floor should be added 

 to the New Museum Building in its central portion, giving a 

 new class-room sixty feet long, and new private rooms for Mr. 

 Balfour's classes, while Mr. Balfour's present class-room could 

 be added to Dr. Foster's department. The cost is estimated at 

 about 1500/. 



The increasing need for a new lecture-room for biology has 

 not been lost sight of ; and it is suggested that it will be advis- 

 able to adapt the present bird-room to the purposes of a lecture- 

 room ; while the Museum of Comparative Anatomy should be 

 extended so as to be capable of accommodating the birds. This 

 alteration would necessarily involve considerable expense, and 

 it is postponed for the present. 



Part I. of the Natural Science Tripos will begin on May 22 ; 

 Part II. on Tune I. 



SCIENTIFIC SERIALS 

 Annalm der Physik und CAemie, No. 3. — Photometric re- 

 searches, by E. Ketteler and C. Pulfrich. — Theory of elliptical 

 double refraction, by E. Lommel. — On differences of tension 

 between a metal and liquids of different concentration, by E. 

 Ketteler. — On galvanic conbinations consisting only of elements, 

 and on the electric conductivity of bromine and iodine, by F. 

 Exner. — Reply to an observation by Herr F. Exner, on Volta's 

 fundamental experiment, by F. Schulze-Berge. — Vaporisation, 

 fusion, and sublimation, by M. Planck. — On new electric figures, 

 and on the gliding of electric sparks, by K. Antolik. — Repre- 

 sentation of longitudinal and transversal waves by projection, 

 by R. Weber. — On the theory of stationary motion, by S. 

 Oppenheim. 



No. 4. — On the relation of transverse contraction to longitu- 

 dinal dilatation in bars of isotropic glass, by W. Voigt. — On 

 the electric resistance of vacuum, by E. Edlund. — Transportable 

 instruments for measurement of variations of intensity of terres- 

 trial magnetism, by F. Kohlrausch. — Tangent-compass for abso- 

 lute measurements, mirror-galvanometer, electro-dynamometer, 

 and magnetometer free of metal, by the same. — Remarks on 

 the mechanical bases of the laws of Ohm and Toule, by E. 



