September 13, 1906 J 



NA TURE 



507 



The specific heats given are, as has been said, those {or 

 constant pressure, and to obtain those at constant volume 

 it is necessary to divide by the constant fe, connecting the 

 specific heats of gases and vapours at constant pressure and 

 constant volume. 



The author gives the values he has used, (i) of the 

 specific heats at constant pressure ; these are taken either 

 from Holborn and Austin's paper, or from Landolt, 

 " Physikalisch Chemische Tabellen," 1905; (2) of the 

 constant k ; these are all taken from Landolt, pp. 407-8 ; 

 (3) of the specific heats at constant volume. 



The specific heats calculated from the above data, of the 

 gases generated by the explosion of the six propellants, are 

 given in the tables embodying the results of the whole of 

 the experiments for each propellant, and in the tables are 

 also given the temperatures of explosion deduced from 

 equations (i) and {2), and here again it must be remem- 

 bered that the temperatures with which artillerists are 

 chiefly concerned are those due to densities varying approxi- 

 mately between 0.17 and 0-23. 



The Italian ballistite, which from equation (i) shows the 

 highest temperature, commences at the density of 005 with 

 4943° C, tliis temperature hardly varying at all until the 

 density of 0-25 is reached, when it slowly but regularly 

 increases to about 5000° C. at d = o.45. Cordite Mark 1., 

 commencing at 4742° C, with a very slight fall, is prac- 

 tically constant up to <i = o-3o, after which it rises somewhat 

 rapidly to a temperature of 4921° C. at ^ = 0-45, and to 

 5065° C. at d = o-50. 



When, however, the temperatures given by equation (2) 

 are reached some very remarkable differences are met with. 

 It is found that at the higher densities and pressures 

 there is generally a very tolerable accordance in the 

 temperatures obtained from the two formulse, but as the 

 density and pressure diminish the divergence becomes in 

 all cases considerable, but very greatly more with the 

 explosives which develop very high temperatures, and 

 which give rise to large percentages of carbonic anhydride. 



The only construction the author is able to put upon 

 the close approximation of temperature given by the two 

 formulae at high densities and pressures, and the wide 

 differences which exist in some of the explosives at low 

 densities, is that at high densities dissociation of the 

 carbonic anhydride is prevented by the very high pressure, 

 and that the great difTerence between, for instance, Italian 

 ballistite and nitrocellulose R.R. at, say, the density of o-i, 

 is due, firstly, to the difference of the temperature at 

 which the nascent gases are generated, and, secondly, to the 

 proportion of CO. which is subject to dissociation. 

 The theory submitted is as follows : — 

 The nascent gases are generated at temperatures approxi- 

 mately as given by equation (i). 



Under the low densities and pressures at the very high 

 temperatures with which we are concerned, the CO, and 

 possibly some H,0 are partially dissociated, giving rise 

 to the fall in temperature exhibited by the results obtained 

 from equation (2) at low densities. At high densities, as 

 already pointed out, the two equations give in some cases 

 accordant results, in all cases tolerable agreement ; it there- 

 fore appears to the author to be reasonable to suppose that 

 the facts he has recorded are due to partial dissociation at 

 low densities and pressures, which dissociation is prevented 

 by the very high pressures ruling at densities of 0.40, 045, 

 and 0-50. 



.^s no free oxygen is ever found in the analyses in cool- 

 ing down, any free oxygen due to dissociation must have re- 

 combined, and the heat lost by dissociation regained. The 



NO. 1924, VOL. 74] 



re-combination must, however, be very gradual, js no dis- 

 continuity is observed in the cooling curves. 



It is then pointed out that a certain amount of confirm- 

 ation is given to the view taken by the fact that if the 

 explosives be arranged according to the amount of heat 

 generated, derived from equation (i), regard being also had 

 lu the amount of CO, found, it will be found that the 

 differences between the two formuUe decrease approximately 

 as the factors to which the author has referred decrease, 

 and a table is given showing these differences. 



" On the Julianiaceae, a New Natural Order of Plants." 

 By W. Botting Hemsley, F.R.S. 



The Julianiacejc comprise two genera and five species. 

 They are resiniferous, tortuously branched, deciduous, 

 dioecious shrubs or small trees, having alternate, exstipu- 

 late, imparipinnate leaves, from about one to three doci- 

 inetres long, clustered at the tips of the flowering branches 

 and scattered along the short barren shoots. The flowers 

 are small, green or yellow-green, quite inconspicuous, and 

 the males are very different from the females. The male 

 inflorescence is a more or less densely branched axillary 

 panicle or compound catkin, from 2J cm. to 15 cm. long, 

 with weak, thread-like, hairy branches and pedicels. The 

 male flowers are numerous, 3 min. to 5 mm. in diameter, 

 and consist of a simple, very thin perianth, divided nearly 

 to the base into four to nine narrow, equal segments, and 

 an equal number of stamens alternating with the segments. 

 In structure and appearance they are almost exactly like 

 those of the common oak. The female inflorescence is 

 similar in structure to that of the sweet chestnut, consist- 

 ing of an almost closed, usually five-toothed involucre, 

 borne on a flattened pedicel and containing three or four 

 collateral flowers, of which the two outside ones are, 

 perhaps, always abortive. 



At the flowering stage, the femjale inflorescences, in- 

 cluding the narrow flattened pedicel and the exserted styles, 

 are about 2 cm. long, and, as they are seated close in the 

 axils of the crowded leaves and of the same colour, they 

 are easily overlooked. The female flowers are destitute of 

 a perianth, and consist of a flattened, one-celled ovary, 

 terminated by a trifid style and containing a solitary ovule. 

 The ovule in both genera is a very peculiar structure. 

 That of Juliania, in the flowering stage, is a thin, flat, 

 obliquely horseshoe-shaped or unequally two-lobed body, 

 about 2 mm. in its greatest diameter, attached to the base 

 of the cell. At a little later stage, in consequence of un- 

 equal growth, it is horizontally oblong, nearly as large as 

 the mature seed, that is, 6 mm. to 8 mm. long, and almost 

 symmetrically two-lobed at the top. A vascular bundle or 

 strand runs from the point of attachment to the placent.-i 

 upwards near the margin into one of the lobes. In this 

 lobe the embryo is tardily developed, and at this stage it is 

 more or less enclosed in the opposite lobe, the relations of 

 the two being as nozzle and socket to each other. It is 

 assumed that the whole of this body, with the exception of 

 the lobe in which the embryo is formed, is a funicle with 

 a unilaterally developed appendage, which breaks up and 

 is absorbed during the development of the ovule into seed. 



The ovule of Orthopterygium is very imperfectly known, 

 but the attachment appears to be lateral and the funicular 

 appendage cup-shaped at the basal end, bilamellate up- 

 wards, and more or less enclosing the embryoniferous lobe. 



The compound fruits of Juliania are samaroid in form, 

 the wing being the flattened pedicel, at the base of which 

 it disarticulates from the undifferentiated part of the pedicel. 

 They vary from 4 cin. to 7 cm. in length by li cm. to 

 2?! cm. in width. Externally they strongly resemble the 

 samaroid pods of certain genera of Leguminosa>, notably 

 those of Platypodium and Myroxylon. The involucre 

 itself, of the largest fruits seen, is only about i cm. deep 

 bv 2 cm. wide. It is composed of very hard tissues, and 

 is quite indehiscent. Only quite young fruit of Ortho- 

 pterygium is known. In this the flattened pedicel is 

 narrow, straight, and equilateral, from 6 cm. to 7 cm. 

 long and about i cm. wide. 



The nuts of Juliania are alrtiost orbicular, biconvex, 

 hairy on the outside, and have a very hard endocarp. The 

 solitary exalbuminous seed is circular or oblong, 6 mm. to 

 10 mm. long, compressed, with a smooth, thin testa. The 

 embryo is horizontal, with thin, plano-convex, more or less 



