4o6 



NATURE 



[Sept. 9, 1875 



hours. The paper called attention to important facts relating to 

 atmospheric pressure, temperature, wind, currents, weather, sea- 

 charts, natural history, earthquakes, &c. The diagrams gave 

 monthly pictures of the Doldrums, showing how in some months 

 they are wedge-shaped, as the late Commodore Maury remarked. 

 The whole paper was a resume of a work about to be published 

 by the Meteorological Office. 



Sir W. Thomson gave an account of the graphical process 

 employed by him and Mr. J. Perry (now professor in Japan) for 

 determining the form of a hanging drop, and other cases of the 

 capillary surface of revolution. 



On account of the interest attaching to the address of the Pre- 

 sident of the Mechanical Section On Stream Lines, and to the 

 fact that as it was being delivered simultaneously with Prof. 

 Balfour Stewart's address only a few members of this Section 

 were able to hear it, Mr. Froude repeated it and the experiments 

 with which it was accompanied again in Section A on the 

 Tuesday morning. One experiment in particular was very inte- 

 resting. A wooden wheel was fixed at a height of about 14 feet, 

 and an endless chain hanging loosely over the wheel in a loop 

 drooped to within 4 feet of the ground. When the wheel with 

 its suspended chain was made to rotate rapidly by means of mul- 

 tiplying gear, the links of the chain symbolised the particles of a 

 running stream ot water. When the chain was struck, while it 

 was rotating, with a wooden mallet, the curved forms into which 

 it was thus beaten were to some extent persistent, as if it 

 v;ere a stiff, fixed wire rope, instead of being a loose chain in 

 motion. Mr. Froude said that this experiment illustrated how 

 water in flowing through pipes did not tend to push them 

 straight, but rather adapted its motions to their curvatures. 



In a letter from Mr. Meldrum, of Mauritius Observatory, 

 written to accompany forty-nine tables (which, however, had 

 not arrived), he expressed an opinion that the evidence adduced 

 in favour of a rainfall periodicity was so strong that he believed 

 we should by and by be able to predict the general character of 

 the seasons. 



Communications were made to the Section by Mr. H. A. 

 Rowland, of John Hopkins University, Baltimore, On (he Mag- 

 netising Function of Iron, Nickel, and Cobalt, and On Magnetic 

 Distribution ; and Mr. A, Malloch explained a method he had 

 found accurate and convenient for producing a sharp meridian 

 shadow. 



On the whole, the physical papers read before the Section were 

 not equal to the average of recent years, either in number or 

 importance ; but, as a compensation, the number of mathematical 

 papers was unprecedented, and the Bristol meeting will be 

 remembered both on this account and for the numerous attend- 

 ance of mathematicians. On the Saturday, which has by custom 

 long been set apart for mathematics, no less than twenty-four 

 papers (including the three reports noticed in another column) 

 on pure mathematics were read. Prof. Cayley explained the 

 theory of the analytical functions which he had termed factions. 

 Sir W. Thomson had three papers all relating to the mathe- 

 matical treatment of the differential equations that occur 

 in I,aplace's theory of the tides. Prof. FI. J. S. Smith 

 explained the effect of the quadric transformation on the 

 singular points of a curve, showing how singularities lying 

 upon one side of the triangle of reference became trans- 

 formed into singularities of a higher order at the opposite 

 angle ; and in another paper of great interest he pointed out 

 the connection between continued fractions and points in a 



line (for example, between "^ expressed as a continued fraction, 



and the order in which the points of section occur if a given line 

 be divided into twenty-four and also into seven parts). Prof. 

 Smith also spoke on the subject of singular solutions. Prof. 

 Clifford's communications related to the theory of linear trans- 

 formations, and one contained a graphical representation of 

 invariants. Mr. J. W. L. Glaisher gave some theorems on the 

 ;/th roots of unity, and explained a formula of verification in 

 partitions, which was founded on and is complementary to one 

 communicated by Sylvester to the Edinburgh meeting in 187 1, 

 viz., that 



"t^i - X ■\- xy - xyz + ...) = o, 



while the theorem in the paper was that 



. -S,(i -^ X + xy + xyz -^^ ...) = Sa"", 

 r being the number of different elements employed in any parti- 

 tion. Mr. H. M. Jeffery's papers related to cubic spherical 

 curves with triple cyclic arcs and triple foci, and to the shadows 



of plane curves oh spheres. Mr. H. M. Taylor's paper con- 

 tained a contribution to the mathematics of the chessboard, and 

 his process enabled him to determine by a mathematical procedure 

 the relative values of the pieces at chess probably as accurately 

 as they admit of being found. Prof. R. S. Ball's communication 

 related to a screw-complex of the second order, and Prof. 

 Everett spoke on motors. Prof. Paul Mansion, of Ghent, had 

 sent two papers, one containing an elementary solution of 

 Iluyghens's problem on the impact of elastic balls, and the other 

 relating to singular solutions. Mr. W. Hayden contributed some 

 geometrical theorems. 



SECTION C— Geology 



After the President's address, a lengthy and elaborate paper 

 on the Northern End of the Bristol Coalfield was read by 

 Messrs. Handel Cossham, PI Wethered, and Walter Saise. 

 The paper was illustrated by many maps and sections. This 

 was followed by a paper by Mr. J. M'Murtrie on moun- 

 tain limestone lying in isolated patches at Luckington and 

 Vobster. The singularity of this case will be realised when it 

 is mentioned that the mountain limestone lies above the coal- 

 measures, which, when originally deposited, overlaid the lime- 

 stone. The Geological Survey examined the ground many 

 years ago, and came, not unnaturally, to the conclusion that the 

 limestone areas were bounded on all sides by faults. Mr. 

 M'Murtrie has been able to show that the coal-measures are 

 continued without disturbance beneath the limestone. The 

 whole thing is inverted, and much interesting talk arose as to 

 the possible movements which could have produced so great a 

 displacement. Mr. Moore, of Bath, followed with an account 

 of the deposits of Durdham Down yielding Thecodont jsaur?/'. 

 The age of the deposit in which this most remarkable Dino- 

 saurian occurs was discussed at some length, but no definite 

 result was arrived at, and the discussion was deferred till 

 Monday. 



Mr. Stoddart described an auriferous limestone found at 

 Walton. The metal was distributed through the mass in 

 extremely minute quantity, and the difficulty of obtaining recog- 

 nisable samples was very great. 



Prof. Hughes's paper, On the Classi/icatioti of the Sedimentary 

 Rocks, began by pointing out that the great divisions are not now 

 drawn where the greatest breaks, all evidence considered, occur 

 in nature. The sequence may be shortly given in these terms. 

 Laurentian — Gap — Labrador Series — Gap [ ? Huronian — Gap] 

 — Cambrian (from red conglomerates of St. David's up to 

 base of May Hill Sandstone)— Gap— Silurian (from May Hill 

 Sandstone = Upper and Lower Llandovery, to top of Red 

 Marls of Sawdde and Horeb Chapel)— Gap — Carboniferous 

 (from bottom of Devonian and Upper Old Red to top of Upper 

 Coal Measures) — Gap — Jurassic (from bottom of breccia and 

 conglomerates of so-called Permian and New Red to top of 

 fluviatile and estuarine deposits of Weald.) The author deferred 

 the full consideration of the rocks above this horizon to a future 

 time, merely commenting on some of the points which seemed 

 to him more especially to call for change. 



In supporting this classification he criticised the division of 

 the May Hill Sandstone into Upper and Lower Llandovery, and 

 commented severely upon the re-naming of these beds, which had 

 been previously correctly described by Prof. Sedgwick under the 

 title May Plill Sandstone. He went into the Cambrian and 

 Silurian controversy at some length, and pointed out that not 

 only was Sedgwick's classification found to be the best in the 

 present state of our knowledge, but that Murchison's had not 

 correctly placed any one of the beds about which he came in 

 collision with Sedgwick. What Murchison then called Caradoc 

 overlapping Llandeilo at Llandeilo, has turned out to be May 

 Hill Sandstone ; what Murchison then called Cambrian under- 

 lying Llandeilo Flags, has turned out to be Caradoc resting on 

 them, ar.d part of the Llandeilo has had to be turned the other 

 way up. The Survey corrected this, and it has appeared corrected 

 in Murchison's later works, but he has never allowed that Sedg- 

 wick was right and he was wrong in 1839. Prof. Hughes 

 thought it was too bad that some should still claim for Murchison 

 the credit of having correctly placed the Ludlow and Wenlock, 

 Caradoc and Llandeilo, but say nothing of the names having at 

 that time been applied to totally different rocks. 



He considered the Devonian and Upper Old Red to have 

 been deposited over a continental area which sunk first on the 

 south : hence the earlier character of the Devonian fauna in the 



