546 



NATURE 



[June 30, 19 10 



presence of liquid particles does cause a certain amount of 

 dissipation, loss of energy is small, and this agrees with 

 observation. On the other hand, with a liquid containing 

 bubbles, damping of vibration is excessive, practically the 

 whole of the wave energy being dissipated in a few wave- 

 lengths or periods. When spheres of liquids are dis- 

 seminated in a gas, compressions and dilatations take place 

 in the latter much as if only the gas were present, and 

 the increased dissipation is due to slight modification in 

 the motion of the gas, brought about by the liquid spheres. 

 In the converse case, when bubbles of gas are disseminated 

 through a liquid, variation of volume consequent on the 

 passage of a wave takes place almost entirely in the gas, 

 and distortion of the liquid about the bubbles of whose 

 volume is the variable introduces a rate of dissipation 

 of a different and larger order. It is pointed out that in 

 a mixture of liquid and gas (in the form of bubbles) the 

 velocity of wave propagation is less than that in either 

 constituent alone, and has a minimum when the propor- 

 tion of gas to liquid has a certain value. If the mixture 

 consists of air and water, minimum velocity of propagation 

 is reached when the volumes of air and water are nearly 

 equal, and is then about one-fourteenth the velocity of 

 sound in air. When the volume ratio of gas to liquid 

 exceeds a certain limit, depending on the order in which 

 the bubbles are arranged, the latter cannot remain 

 spherical, and the mixture then becomes a froth, or collec- 

 tion of air cells separated by thin liquid walls. It is 

 shown by experiment that such froth is a very effective 

 agent in damping vibrations. — Prof. P. V. Sevan : The 

 dispersion of light by potassium vapour. The work 

 described in this paper was an attempt to measure quanti- 

 tatively the amount of dispersion in the vapour of 

 potassium. Dispersion takes place in the vapour chiefly on 

 account of the red absorption lines, but is also to a smaller 

 extent due to other lines of the principal series. !Measure- 

 ments were made showing dispersion affected by the first 

 six pairs of lines of the principal series, and an effect 

 could just be detected at the next pair of lines. The dis- 

 persion was found to lit a Sellmeier formula, and values 

 for four of the constants for this formula were obtained. 

 On theoretical grounds we can conclude, from the relative 

 values of the constants of the dispersion formula, that the 

 number of atoms taking part in the absorption of the light 

 after the first pair of lines must be only a small fraction 

 of the total number present in the vapour, and that this 

 fraction decreases with the number of lines in the series. 

 It is suggested that the explanation of series lines must 

 therefore be looked for in systems which are not the atom 

 pure and simple, but probably atoms to which a corpuscle 

 or more than one corpuscle become attached. Several 

 types of quasi compounds may thus be formed in a way 

 suggested by Sir J.J. Thomson, and the periods commonly 

 associated with the atoms may be the periods of these 

 systems. Our conception of the atom may be thus con- 

 siderably simplified, as the number of degrees of freedom 

 for each individual atom may be diminished very largely 

 if this view be the true one. — J. W. Gifford : Additional 

 refractive indices of quartz, vitreous silica, calcite, and 

 fiuorite. — J. Ivon Graham : The absorption spectra of 

 sulphur vapour at different temperatures and pressures, 

 and their relation to the molecular complexity of this 

 element. The absorption spectra were photographed at 

 temperatures varying from 530° C. up to 900° C, at 

 atmospheric pressure, and at constant temperatures, under 

 pressures between atmospheric and 10 mm. of mercury. 

 The photographs at constant pressure with the above 

 variation of temperature show the presence of two distinct 

 absorption spectra ; these are attributed to the intra- 

 molecular vibrations of the Sg and S, complexes re- 

 spectively, the former producing a series of absorption 

 bands between n( = A-')20oo and 112600, with mean posi- 

 tion of maximum absorption about n 2500, whilst the 

 relatively lighter S^ molecular system, by taking up vibra- 

 tions of greater frequencies, produces a series of bands 

 lying between, n 2900 and 1x3820, with mean position of 

 maximum absorption about n 3750. Since only two dis- 

 tinct spectra are evident, it is concluded that the equation 

 S,, = 4S, represents the sole reaction that occurs in the 

 dissociation of sulphur vapour on heating from its boiling 

 point up to qoo° C. The interpretation of the photographs 

 of the absorption spectra of the vapour at different (con- 

 NO. 2122, VOL. St,'] 



stant) temperatures, but with reduction of pressure, 

 indicates that above 580° C. the dissociation of the mole- 

 cule S, is simple, that is, there is direct dissociation into 

 S, complexes, but at or below 520° C. the dissociation 

 takes place with the formation of molecules intermediate 

 in complexity between the above two aggregates. The 

 position of maximum absorption of each band is towards 

 the more refrangible edge, whilst the individual bands of 

 each series appear to become stronger, also in the more 

 refrangible direction. The two series of bands are shown 

 mapped in oscillation frequencies, the similarity between 

 the series being much more evident when illustrated in 

 this manner. Reproductions of photographs also accom- 

 pany the paper. — Dr. T. H. Havelock : The wave-making 

 resistance of ships : a study of certain series of model 

 experiments. In a previous paper (Proceedings, A, vol. 

 Ixxxii., p. 276, 1909) the author discussed the variation of 

 the wave-making resistance of a ship with its speed, and 

 a formula was obtained by specifying the action of a ship 

 in terms of a simple equivalent pressure distribution 

 travelling over the surface. The present investigation is 

 a more systematic study of some of the coefficients of the 

 formula, the experimental data being taken from published 

 records of tank experiments with models. The discussion 

 is limited to types for which the resistance-velocity curve 

 shows clearly the humps and hollows which are usually 

 ascribed to interference of wave systems originating at the 

 bow and stern ; the tabulated results form a numerical 

 study of the latter theory, and exhibit the variation of 

 the 'coefficients of the simple equivalent pressure system 

 with the displacement of the model, the proportion of 

 parallel middle body, and various coefficients of fineness. 

 Without attempting to express the coefficients by empirical 

 formulas, sufficient information is available to allow of an 

 approximate estimate of their values in similar models ; 

 this is illustrated by the Ttirbinia, and the result is dis- 

 cussed in relation to the published record of trials of that 

 vessel. The characteristic interference effect mentioned above 

 appears to occur specially in rather full-ended models, with 

 fairly high cylindrical coefficients ; in this case it is per- 

 missible to regard the equivalent pressure system as having 

 two parts associated with the bow and the stern re- 

 spectively. An examination of models with finer ends 

 suggests that this simple interference theory is inadequate 

 in certain cases ; the study of a modified type of pressure 

 distribution is indicated. — Dr. Georges Dreyer and W. 

 Ray : The blood volume of mammals as determined by 

 experiments upon rabbits, guinea-pigs, and mice, and its 

 relationship to the body weight and to the surface area 

 expressed in a formula. The blood volume of animals has 

 for many years been the subject of numerous investiga- 

 tions. This is but natural considering its great import- 

 ance for the study of disease. As, however, the results 

 obtained are very discordant, the authors have determined ^ 

 the blood volumes of rabbits, guinea-pigs, and mice by 

 Welcker's method, by washing out the circulatory system 

 and by following the percentage fall of haemoglobin after j 

 bleeding. The experiments of the authors have given the j 

 following results : — (i)The blood volume of living mammals j 

 can be determined very accurately by bleeding the animal ' 

 (about 20 per cent, of its original blood volume) and deter- j 

 mining the percentage fall of hjemoglobin at the moment! 

 when equilibrium is reached. This method gives results re- 

 markably concordant with those obtained by w-ashing out 

 the circulatorv system. In employing this method it is 

 absolutely essential that the animals should not have been 

 bled before. (2) In normal healthy mammals (rabbit, 

 guinea-pig, and mouse) the blood volume is satisfactorily 

 expressed by the following formula, B = Wr//c. where B is 

 the blood volume in cubic centimetres, W the weight of, 

 the individual in grams, and 7c a constant to be ascertained ! 

 for each particular species of animal. This formula \ 

 indicates that the smaller animals of any given species, 

 which have a relatively greater body surface than heavier 

 ones, have also a relatively greater blood volume. That is 

 to say, the blood volume can be expressed as a func- 

 tion of the surface area. It is therefore misleading to 

 express the blood volume as percentage of the body w-eight, 

 as has hitherto been invariably done. (3) The constant k, 

 bv means of which the blood volume in cubic centimetres 

 can be calculated from the formula B=_W'/7o when the 

 weight of the animal in grams is Ivnown, is approximately, 



