478 



NATURE 



[Marc/i 1 8, 1886 



pleteness of the assumptions on which these equations are 

 founded ; and the result of the whole research is to point to a 

 conclusion (important to natural philosophy) that not only in 

 cases of intentional lubrica'ion, but wherever hard surfaces under 

 pressure slide over each other without abrasion, they are separ- 

 ated by a film of some foreign matter, whether perceptible or 

 not ; and that the question as to whether the action can be con- 

 tinuous or not turns on whether the motion tends to preserve 

 the foreign matter between the surfaces at the points of pressure, 

 as in the almost if not quite unique ca^e of the revolvin_^journaI, 

 or tends to remove it, and sweep it on one side, as in the action 

 of all backward and forward rubbing with continuous pre.-sure. 



The fact that a little grease will enable any surfaces to s'ide 

 for a time has tended doubtless to obscure the action of the 

 revolving journal to maintain the oil between the surfaces at the 

 point of pressure, and yet, although only now understood, it is 

 this action that has alone rendered machinery or even carriages 

 possible. The only other self-acting system of lubrication is that of 

 reciprocating motion with intermittent pressure and intermittent 

 separation of the surfaces to draw the oil back or to draw a 

 fresh supply. This is important in certain machinery, as in the 

 steam-engine, and is as fundamental to animal mechanism as is 

 the continuous lubricating action of the journal to mechanical 

 contrivances. 



Mathematical Society, March ii. — Mr. J. W. L. Glaisher, 

 F.R.S., President, in the chair. — Mr. L. J. Rogers was ad- 

 mitted into the Society. — Prof Sylvester, F.K.S., read a paper 

 on an instantaneous proof of the expression for the number of 

 linearly independent invariants or seminvariants of a given 

 type, and also of the corresponding e.\pression for reciprocants. — 

 Mr. E. B. Elliott read a paper on ternary and «-ary recipro- 

 cants, and Mr. L. J. Rogers read one entitled " Homograi.ihic, 

 Circular, and Projective Reciprocants." — Capt. P. A. Mac- 

 mahon, R. A., communicated a proof of Cayley's fundamental 

 theorem of invariants, and Mr. Leudesdorf communicated a 

 note by Mr. Griffiths, on the invariantisers of a binary quantic. 

 — Mr. Tucker (Hon. Sec. ) called the attention of the Society 

 to a paper read before the Royal Irish .Academy (January 26) 

 by T'r. Casey, F.R.S., entitled "On the Harmonic H._-xagon 

 of a Triangle, ' in which properties established by himself for a 

 harmonic quadrilateral were beautifully generalised and extended 

 to the harmonic hexagon and other harmonic polygons. The 

 hannonic hexagon is thus defined : — A i> C is any triangle, 

 A A', S B', C C its ."-ymmedian lines, which meet the circum- 

 circle in A' B' C ; the figure A B' C A' B C is the harmonic 

 hexagon. Dr. Casey calls the triangles A' B' C, A B C co- 

 symmedian triangles. — Mr. Tucker then communicated, for the 

 Rev. T. C. Simmons, the following extensions :— Let A" be the 

 inverse point of the symniedian point K with respect to the 

 circumcircle, and let A"' A, K' B, K' C meet this circle in 

 A" B" C" ; then .-i" />'" C" may be called the inverse cosymnic- 

 dian triangle of A B C. What Dr. Casey has proved for co- 

 symmedian triangles, Mr. Simmons shows also for these inverse 

 triangles, and the result is that the three sets of triangles have 

 the same Brocard points, symmedian point, Brocard, "T. R.," 

 sine and cosine circles. — Mr. Simmons also sent a construction 

 for finding a triangle whose Brocard points and angle are given, 

 whence he proves that anv triangle inscribed in a certain circle 

 and circumscribed to the Brocard ellipse has the given Brocard 

 points for B. points. 



Linnean Society, March 4. — Sir John Lubbock, Bart., 

 F.R. S., President, in the chair. — Messrs. Gilbert C. Bourne, 

 William H. Catlett, and Thos. A. Cotton were elected Fellows 

 of the Society. — One of nine volanies of water-colour drawings 

 of British plants, by the late Miss Mose!ey of Great Malvern, was 

 exhibited for Miss Onslow. — .A paper on Strotigylus Ariij'uidi 

 and S. tetrccanthus, by Prof. Spencer T. Cobbold, was read, 

 and specimens illustrating the encysted stage of the latter ex- 

 hibited. Of -Arnfield's strongyle he drew attention to the morph- 

 ology of the hood and its rays, the po.'-ition of the vulva, and the 

 structure of the embryo, contrasting these with those of allied 

 forms. Regarding his observations on the four spined strongyle 

 these may be sununarised as follows : — (l) The eggs are expelled 

 from the parent in a state of fine yolk-cleavage ; (2) embryos 

 are formed after egg expulsion, and a few days subsequently 

 escape from the envelopes, undergoing a primary change of skin 

 in moist earth during warm weather ; (3) thereafter they live 

 many weeks as rhabdiform nematoids ; (4) in all likelihood an 

 intermediary host is unnecessary; (5) the rhabdiform larvK are 



passively transferred to their equine bearers either with fresh-cut 

 fodder, or while the animals are grazing ; (6) transferred to the 

 intestinal canal they enter the walls of the Citcum and 

 colon, encjst themselves, and undergo change of skin ; 



(7) their presence in the intestinal walls is associated with 

 certain pathological conditions, frequently fatal to the bearer ; 



(8) ordinarily the young worms perforate their cysts and 

 migrate to the lumen of the bowel, and indications of sex 

 appear at this the " Trichonema stage"; (9) they next form 

 cocoons by agglutination of vegetable debris within the gut, 

 and undergo a third skin-casting, with intestinal metamorphosis ;' 

 (10) lastly, their internal sexual organs and the completion of 

 definite form are acquired within the colon of the host. — A paper 

 was read by Mr. G. Murray on a new species of lihipilia from 

 the Mergui Archipelago. This was collected by Dr. J. Ander- 

 son (of Calcutta Museum) in 1SS2, and recently presented to the 

 British Museum. It was found growing on mud flats at King's 

 Island Bay. The genus Rhipilia was established by Kiitzing 

 for the reception of two species — R. tomentosa and A*, ion^icaulis 

 — collected by .Sonder in the .\ntilles. To these Prof. Dickie 

 added A. Ransoni from Barbadoes. The new species, R. Anier- 

 soni, differs from the two former in the frond being completely 

 sessije on the mass of rhizoids, and from the latter in the sessile 

 frond being entire. A hitherto unidentified, imperfect specimen 

 brought by Cumming from the East (Philippines?) is now found 

 to be identical with Dr. -\nderson's example, which is well pre- 

 served in spirit, and thus the Oriental habitat of the genus is 

 corroborated. The author describes minutely and illustrates the 

 remarkable rhizoid filaments of R. AnJcrsoni. — A second paper 

 was read by Mr. G. Murray, viz. on two new species of 

 Leii/inus, one of them growing on a large Sclcrotiiim. — Mr. J. 

 G. Baker afterwards gave orally the gist of a communication on 

 a collection of ferns made in North Borneo by the Bishop of 

 Singapore and Sarawak. 



Physical Society, February 27. — Dr. J. H. Gl.adstone in 

 the chair. — Dr. Sydney \'oung and Mr. D. E. Jones were 

 elected members of the Society. — The following communications 

 were read : — The relations of pressure, temperature, and voluo.e 

 in s.aturated vapours, by Prof W. C. Unwin. In the first part 

 of this paper certain formula given by Messrs, Ramsay 

 and Young in a recent communication on some thermo- 

 dynamical relations are criticised. The most important 

 of these is the statement that for different saturated vapours 



at the same pressure P'T,'^^ constant. Prof. Unwin finds, 



dp dp t- dp 



however, that /,, is less constant than fi t, while- ^. 



' di dt' p dt 



is nearly a constant quantity for all saturated vapours under 

 any conditions. This result suggested that 



'111 dp 

 p dt 

 might be more nearly constant, and the integration of this 

 gives 



log * = fl- _ 



a formula to the examination of which the second part of the 

 paper is devoted. From it maybe derived the following rela- 

 tions in which for convenience in calculation the logarithms 

 given are to the base 10. 



2-3025 



log/)' 



b"- 



£-.''/ =2 '3025^, 

 /• dt "> \ 



&e. These formulaa have been examined in the case of steam 

 from - 30° to 230° C, and with pressures varying from '4 to 

 20,000 mm. The constants were found to be 



« = 7-5030 ... ^ = 7579 - «=i-2S, 

 and the difterences between the calculated results and the obser- 



