ii6 



NATURE 



[May 29, 1890 



these seed-stems. The wind was, in this return journey, in such 

 a direction as to favour the tendency of the burning grass to set 

 fire to the carriages. They caught fire. About eight persons 

 were totally consumed, hardly even bones being found to tell 

 the tale ; and eighteen escaped up the banks in a pitiable con- 

 dition. I do not know how many of these are now alive. 



W. Larden, 



■ON THE PROPERTIES OF LIQUEFIED GASES 

 V/r E. MATHIAS has just published in the form of an 

 '■^^ • inaugural thesis (Gauthier-Villars, Paris), an important 

 investigation on the latent heat of vaporization of liquefied gases. 

 The value of this coefficient for sulphurous acid, carbonic acid, 

 and nitrous oxide was determined experimentally throughout a 

 considerable range of temperature by the following method. 

 The gases were first liquefied in a small copper cylinder, 9 cm. 

 in height, 3 cm. in diameter, with walls 0-38 cm. in thickness. 

 The cylinder was then weighed and introduced into an ordinary 

 Berthelot calorimeter, and the liquefied gas was allowed to 

 evaporate slowly, the pressure being constantly read off on a 

 Bourdon gauge and regulated by means of two conical screw 

 taps. The calorimetrical method employed was a null one 

 (devised by the author), the heat absorbed by the evaporation of 

 the liquid being compensated for by adding sulphuric acid of 

 known strength to the water in the calorimeter, at such a rate as 

 to keep its temperature approximately constant. The total 

 amount of heat absorbed was thus easily determined, while the 

 correction for cooling was reduced to a minimum. When 

 necessary the laboratory was heated by means of regulated 

 gas-burners, so that the liquid in the calorimeter and the sur- 

 rounding atmosphere were at the same temperature in all cases. 

 Seven experiments on liquid sulphurous acid between the 

 temperatures of + 5°74 and + I9°'95 gave values for L, the latent 

 heat of vaporization, which may be expressed by the empirical 

 formula — 



L = (91 '87 - 0-384;' - 0-000340/"-) Cal. 

 Nineteen experiments on liquid carbonic acid between + 6°'65 

 and + 30° -82 may be expressed by the formula — 



JJ = [117-303 (31 -^) - 0-466 (31 -f)-] Cal. 

 The numbers obtained afford a satisfactory verification of 

 Clapeyron's formula, as calculated from constants previously 

 determined. 



Owing to the great difficulty of obtaining nitrous oxide free 

 from nitrogen, the results obtained with this gas can only be 

 regarded as qualitatively correct. But the graphic representation 

 of fifteen experiments, performed between the temperatures of 

 + 5°'37 ^nd -f 34°, show that the curve representing the variation 

 of the latent heat with the temperature is exactly of the same 

 form for nitrous oxide as for carbonic acid. In both cases the 

 tangent to the curve at the critical point is rigorously perpendicular 

 to the temperature axis. We may from this c.:)nclude that at the 

 critical point L is rigorously equal to zero, and hence from 

 ■Clapeyron's formula that the specific volume of the liquefied gas 

 and its saturated vapour are rigorously equal, a fact questioned 

 lately by Cailletet and Colardeau. It follows, moreover, from the 

 thermodynamical equation — ^ 



m' = in + dLjdf - L/T, 



where m' is the "specific heat of the saturated vapour" — that 

 at the critical point, 



in' = - 00 , 



Now at the temperatures at which experiments have been made 

 ■on ordinary liquids (water, ether, acetone, &c. ), m', though 

 negative, was found to increase with rise of temperature ; but 

 since we may conclude from these experiments that near the 

 critical point it will decrease, it follows that it must at some 

 intermediate temperature pass through a maximum. It follows 

 also that if m', while increasing, pass through a zero value, that 

 it will pass through a second zero value in the opposite sense. 

 As m' for carbonic acid and nitrous oxide is negative and 

 decreasing between - 50° and + 30°, if a zero value exist for these 

 gases, it must be at a very low temperature. In the case of 

 sulphurous acid, the results obtained were shown to confirm 

 certain formulae given by Bertrand in his "Thermodynamique," 

 and applicable to saturated vapours at temperatures much below 

 the critical point. The memoir as a whole is masterly. 



I See Verdet, "TWorie Mecanique de la Chaleur," i. p. 258. 



NO. 1074, VOL. 42] 



NOTES ON INDIAN INSECT PESTS. 



T 



HE Government of India has evidently begun to reali/.e the 

 importance of the study of injurious insects, and the 

 methods of combating them. Some time ago, Mr. E. C. Cotes, 

 of the Indian Museum, published the first two numbers of 

 " Notes on Economic Entomology," dealing respectively with 

 the wheat and rice weevil in India, and with insecticides and the 

 methods of applying them. This series has been discontinued, 

 and its place has been taken by " Notes on Indian Insect Pests." 

 The first number of the new series contains notes on the Rhyfi- 

 chota, by Mr. Atkinson, the most detailed of which deals with the 

 rice sapper {Leptocorisa acuta). These insects settle on the rice ear, 

 sometimes to the number of ten on one ear, and, extracting the 

 milky juice of the grain, leave the husk dry. Unfortunately, 

 nothing is known of the life-history of this pest. Mr. Atkinson 

 also describes a new genus and species of Coccidae {Psetido- 

 pidvinaria sikkimensis), found on the under surface of the leaves 

 of oaks, chestnuts, and cinchona : hitherto this has not appeared 

 in sufficient numbers to effect much damage. 



Mr. De Niceville contributes an account of two injurious 

 butterflies : one, which he identifies as Suastus grcmius, devours 

 the young and tender rice-shoots in the paddy-fields, but for- 

 tunately avoids the more mature plants. As a preventive for 

 this pest, Mr. De Niceville recommends raising the earthen walls 

 round each plantation, so as to completely submerge the rice ; 

 this would prove fatal to all stages in the life-history of the 

 butterfly, with the doubtful exception of the eeg. The other 

 report deals with Lampides elpis, whose larva devours the buds 

 and young fruit of the Cardamom. Many allied forms have a 

 gland on the eleventh segment, secreting a sweet fluid, much 

 sought after by ants, but this seems to be absent in the species 

 here described. 



The remainder of the number is made up of thirteen reports 

 and numerous short notes contributed by Mr. Cotes. Two of 

 these reports are extensions of his " Notes on Economic Ento- 

 mology," mentioned above. No mention is made of the Straw- 

 sonizer, whose value as a disseminator of insecticides has recently 

 been recognized in England. The remaining eleven deal 

 with caterpillars which attack the tea plant, sal trees, rice, 

 Cedrela toona, sugar-cane, sorghum, and the blankets belonging 

 to the Army Clothing Department, and with various species of 

 beetle injurious to the rice, bamboo, mango, and shorea tree. 

 The beetle, which lives under the bark of the last-mentioned 

 tree, closely resembles the Tomicus chakograplms, which is so 

 injurious to the spruce in Europe. 



The notes which conclude the work are often very frag- 

 mentary, but are full of suggestion, and there is no room to 

 doubt that the lacunae in the life-history of the insects with 

 which they deal will soon be filled up, now that the authorities 

 of the Indian Museum have provided a journal which will 

 prove a means of intercommunication between the numerous 

 entomologists and cultivators scattered over India. 



The number is illustrated by four good plates of photo-etchings 

 executed in Calcutta. A. E. S. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — An elector (who must be a Head of a College) 

 to the Sadlerian Professorship of Mathematics will be elected 

 by the resident members of the Senate on June 3, from i to 2 

 p.m. The vacancy is caused by the death of Dr. Phelps, 

 Master of Sidney Sussex College. 



A. R. Forsyth, F.R.S., the author of the well-known 

 "Treatise on Differential Equations," has been approved for 

 the degree of Doctor in Science. 



Dr. Hill, Master of Downing College, announces a class in 

 Practical Histology, to be held during the Long Vacation.^ 



The General Board of Studies recommend that the stipends 

 of the following teachers of science be increased : — Mr. Gadow, 

 King's College, Lecturer in Advanced Morphology, from ;!^ioo 

 to ^'150 ; Mr. Marr, St. John's College, Lecturer in Geology, 

 from ^'lOOto^iSO ; Mr. Harker, St. John's College, Demon- 

 strator in Geology and Lecturer in Petrology, from ;^ioo to 

 £1^0; Mr. Barber, Christ's College, Demonstrator in Botany, 

 from 2^100 to ;^i5o ; an additional Demonstrator in Chemistry 

 at a stipend of ^100. 



A conference on the local lectures under the University 



