Feb. 4, i886]r 



NA TURE 



335 



to examine only one, and of tlie four the third is in the form that 

 can be most readily tested. This law, the statement of which 

 is, that for all substances at any given pressure the product 



A^ is constant, / being the pressure, and /the absolute tem- 



dt 

 perature of saturated vapour at that pressure, is represented 

 mathematically thus — 



<* = </>{/) (■) 



(it 



'p{t) being a function of the pressure, independent of the 



substance. Writing this equation 



dp _ dt 



and integrating, we get 



t = a<^(p) (2) 



v|/(/) being also a function of the pressure only, and a a constant 

 depending only upon the substance employed. It is in this form 

 ihat the authors have examined the third law ; if true, it follows 

 at once from (2) that the ratio of the temperatures of two 

 saturated vapours to one another at any pressure is the same as 

 the ratio at any other pressure. It is seen, however, either by 

 reference to Regnault's numbers, or Rankine's formula — 



log/ = ,/ - ^ - Z - . . . 



an expression based upon his molecular theory, and which, as 

 remarked by one of the authors at the last meeting, agrees with 

 Regnault's results with remarkable closeness, that this ratio is 

 far from constant. The authors are therefore compelled to con- 

 clude that the expressions given by Prof. Ramsay and Dr. 

 Young must not be regarded as absolute laws. — A note on the 

 paper by Prof. J. W. Clarke on the determination of the heat- 

 capacity of a thermometer, by Mr. A. W. ^ Clayden. The 

 author has applied a correction to an expression given by the 

 late Prof. J. W. Clarke for measuring the heat-capacity of a 

 thermometer, in a paper communicated to the Society at a 

 previous meeting (April 25, 1885). Prof. Clarke's expression 

 was affected by the mercury not entirely filling the bulb and 

 stem of the thermometer. The corrected expression obtained 

 liy the author is 



V - ^(^ - '-^^ 

 "^1 - , s„(i + 0) 



.(, s^, and Jj being the mean densities of the instrument, mercury, 

 and glass respectively, j8 and o the coefficients of voluminal expan- 

 sion of mercury and glass, Kand F^ the volumes of the instrument 

 and of the mercury. — Note on some organic substances of high re- 

 fractive power, by Mr. H. G. Madan. In the course of some 

 correspondence respecting M. Bertrand's polarising prisms, the 

 author was informed that the cement used was napthyl-phenyl- 

 ketone dibromide. He has consequently prepared specimens of 

 the ketone, and subjected them to optical examination. The 

 ketone is a thick yellow oil, boiling at a temperature near the 

 boiling-point of mercury ; it appears to be a very stable, neutral, 

 and harmless substance like Canada balsam, but unfortunately it 

 does not appear to be capable of hardening, and hence is not by 

 Itself adapted for a cement. Its refractive index for the D line 

 IS I '666, higher than that of carbonic sulphide, while its dis- 

 persive power is approximately the same as that of that 

 sub-stance. The author has made the bromide of the ketone 

 referred to above, but it seems liable to decompose with forma- 

 tion ofhydrobromic acid, which acts upon the spar. Mr. Madan 

 also exhibited a specimen of metacinnamene, a highly refracting 

 ^Lass-like solid obtained by the action of light or heat upon 

 cinnamene. This substance possesses a refractive index of 

 I "593 for the D line, and would make a valuable cement if it 

 showed a firm adhesiveness for glass. — The Pre^ident exhibited 

 and described an instrument he had made in the course of an 

 acoustical investigation upon which he had been engaged. It is 

 a musical instrument similar in principle to the harmonicon. In 

 the case of the harmonicon the rectangular plate is usually sup- 

 ported by strings passing through the nodes, but the author 

 wished to make an instrument that could be "bowed." The 

 "nodes" are not absolute positions of rest, the particles at them 

 describing curves having cusps pointing outwards. The plan 

 adopted was to solder two springs to the plate, which was of 

 brass, the points of attachment being slightly outside the nodes, 



and the springs being such as to give the same fundamental note 

 as the plate. The other ends of the .springs were attached to 

 the mouth of a resonator whose fundamental note was also that 

 of the plate. The plate when struck or bowed gave a tone very 

 like that of a timing-fork, and in a discussion th.at followed, 

 Prof. .S. P. Thompson sugge-ted the possible use of these instru- 

 ments as a substitute for a series of forks the cost of a complete 

 set of which often places them beyond the reach of the student. 

 Prof. McLeod suggested that the springs should be tuned to the 

 octave of the plate instead of to its fundamental, and that they 

 should have a slightly different form. 



Edinburgh 

 Royal Physical Society, January 20. — Prof. Turner, 

 F.R.S., President, in the chair. — Obituary notice of the late 

 Dr. Carpenter, by Prof. Ewart.— The President read a paper 

 on the occurrence of the bottle-nosed whale f^Hyperoodon 10s- 

 tralus) in the Scottish seas. After a review of the history of 

 this whale. Prof. Turner proceeded to describe several speci- 

 mens which had come under his observation, more especially a 

 yoimg male, caught at Dunbar in November 18S5. He then 

 compared the external characters of Hyperoodon, Mesoplodon, 

 Ziphius. A detailed description of the rudimentary teeth in 

 the upper and lower jaws of Hyperoodon was also given, and 

 the periods of the year when this animal migrated .southwards 

 and northwards were referred to.— Mr. Brook read a paper on 

 the relation of yolk to blastoderm in fish-ova. The author 

 endeavoured to show that the function of the cortical protoplasm 

 surrounding the yolk (the parablast) is primarily a digestive one. 

 The existence of this layer is a necessary consequence of the 

 separation of yolk from protoplasm in meroblastic ova. The 

 material thus elaborated in the [parablast is undoubtedly 

 budded off in the forni of cells. It has been asserted by Hoff- 

 mann and others that these take no part in the formation of 

 the embryo, but are used up in the temporary circulatory system 

 around the vitellus. In the herring, cod, Trachinus, and pro- 

 bably the whole group of pelagic ova, there is, however, no trace 

 of a vitelline circulation, yet cells are produced in the parablast 

 of these forms in the same manner as in the trout. There thus 

 appears no alternative but that the cells must take part in the 

 formation of the embryo. It was therefore argued that, from a 

 consideration of the physiological function of the parablast, the 

 morphological value of this layer is more important than has 

 been hitherto admitted.— A note was communicated from Mr. 

 Dendy, on an abnormal specimen of Comatula (which had 

 twelve arms) from the Firth of Clyde ; Mr. Raeburn read ex- 

 tracts from his journal on the birds of the Shetland Islands ; 

 and Mr. Muirhead exhibited a sj^ecimen of the Glossy Ibis 

 {Jbis fascinellus) shot last September on the borders of Rox- 

 burghshire, and a Garganey shot last February in Berwickshire. 



Dublin 

 Royal Society, December 16, 1885.— Physical, Experi- 

 mental, and -Applied Science Sections.— Sir Robert W. Jackson, 

 C.B., in the chair.— On the description by points of the prin- 

 cipal caustics of a circle, by G. Johnstone Stoney, D.Sc, 

 F.R.S.— Meteors and meteorites, by W. H. S. Monck, M.A. 

 —On the fog-penetrating power of the double quadriform burner, 

 by Prof. W. F. Barrett. The author described the results of 

 some experiments recently made to test the illuminating power 

 of Mr. Wigham's latest adaptation of gas to lighthouse illu- 

 mination. The double quadriform burner consists of a series of 

 four superposed 8S-jet gas-burners placed alongside of four 

 similar superposed burners. The eight burners are in one plane, 

 parallel to which, and at the proper focal distance, are placed 

 eight annular lenses on one side, and a similar set of lenses on 

 the other side. The lights blend into one at a distance of about 

 1500 feet from the lighthouse. Experiments were made on two 

 evenings, both of which were foggy. On the second evening 

 the fog was so dense that a powerful revolving light less than 

 half the distance of the double quadriform was entirely cut off, 

 and the sound of a large fog-siren, driven by a gas-engine and 

 placed alongside the experiment.al light, was also extinguished 

 by the fog ; nevertheless, on both occasions the double quadri- 

 form was easily seen by the naked eye, and its position readily 

 determined, at six miles' distance. The author expressed his 

 unqualified satisfaction at the result of his observation, and 

 hoped that the authorities at Trinity House would be^ induced 

 to come to Dublin and judge for themselves of the merit of Mr. 

 Wigham's invention. 



