130 



DEVELOPEMENT OF THE VIVIPAROUS APHIDES. 



[1854 



whether we consider them in reference to volumes or to weights. 



2. The capacity for heat of atmosphere air (that of wa'ter=l) 

 is 0-2609; that of the vapour of water 0-8470. 



3. The specific heat of equal volumes of atmospheric air 

 increases with the density, but in a less rapid progression. The 

 ratio of the pressures being 



1 1 



that of the specific heat is 



1-3583 



1-2396. 



4. De la Roche and Berard admit, on theoretic considerations, 

 and resting, moreover, on direct experiments of Gay-Lussac, that 

 the specific heat of the gas increases rapidly with the temperature. 



These are the most precise notions on the specific heat of gases 

 which we at present possess, and which are generally admitted 

 by physicists. The limits within which I am obliged to confine 

 myself, in the present extract, prevent me from discussing the 

 methods which have been adopted by my predecessors, or to 

 explain those which I have myself followed. I will merely say, 

 that I have met, in this kind of researches, great difficulties, not 

 only in the experiments, but also in point of theory ; the con- 

 siderations which I have mentioned at the commencement of 

 this article will render them easily understood. 1 bus, although 

 my first experiments are fifteen years old, and although I 

 announced them at that epoch in the Memoirs on the Specific 

 Heals of Solids and Liquids, it is only after using the most 

 various methods, and after having forced the elements of their 

 correction in opposite directions, that I now, with confidence, 

 present my results to the Academy. 



According to my experiments, the specific heat of air, com- 

 pared with that of water, is 



Between — 30° and 10° cent. 02377 



" + 10° " 100° .. 0-2379 



" 100° " 225° .. 0-2376 



Thus, contrary to the experiments of Gay-Lussac, the specific 

 heat of air does not vary sensibly with the temperature. 

 Experiments made upon some other permanent gases led to a 

 similar conclusion. 



In experiments made upon atmospheric air, under pressures 

 Varying from 1 to 10 atmospheres, I found no sensible difference 

 between the quantities of heat which the same mass of gas 

 abandons in cooling, through the same number of degrees. 

 Thus, in contradiction to the experiments of De la Roche and 

 Berard, who found a very notable difference for pressures vary- 

 ing only from 1 to 1-3 atmospheres, the specific heat of the 

 same mass of gas is independent of its density. Experiments 

 made upon several other gases led me to analogous conclusions. 

 I, nevertheless, present this law with some reserve ; I cannot yet 

 decide whether the capacity for heat under different pressures is 

 absolutely constant, or whether it undergoes a very slight varia- 

 tion ; because my experiments, perhaps, require a slight correction 

 for the state of motion in which the gas was. 



The specific heat 0-237 of the air, compared with water, is 

 notably smaller than the number 0-2669, admitted by De la 

 Roche and Berard ; it is derived from more than a hundred 

 determinations made under different conditions. 



The other elastic fluids whose specific heat I have determined 

 are — 





Specif. 



c heats. 





Simple gasei. 



By weight. 



By volume. 



Densilips. 



Oxygen 



0-2182 . 



.. 0-2412 . 



. 1-1056 



Azote (nitrogen) 



0-2440 



. . 0-2370 . 



. 0-9713 



Hydrogen 



3-4046 



.. 0-2356 . 



. 0-0692 



Chlorine 



0-1214 



. . 0.2962 . 



. 2-44 



Bromine 



0-05518 . 



.'. 02992 . 



. 5-39 



In casting the eyes over this table, it is immediately remarked 

 that the specific heats of equal volumes of oxygen, azote, and 

 hydrogen, differ very little from each other; so that we would be 

 led to admit that the specific heat of the simple gases is the 

 same, when these gases are taken under the same volume and at 

 the same pressure. But for chlorine and bromine, numbers have 

 been found nearly equal to each other, but much greater than 

 those which were obtained for the other simple gases. 



Specific heata. 



CompoilT 



id crises. 



By weight. 



By volume. 



Densities 



Protoxide of azote . . 



0-2238 



.. 0-3413 



.. 1-5250 



Deutoxide 





0-2315 



.. 0-2406 



.. 1.0390 



Oxide of 



carbon 



0-2479 



.. 0-2399 



.. 0-9674 



Carbonic acid 



0-2164 



.. 0-3308 



.. 1.5290 



Sulphuret 



of carbon 



0-1575 



.. 0-4146 



.. 2-6325 



Sulphurous acid 



0-1553 



.. 0.3489 



.. 2-2470 



Chlorhydric " 



0.1845 



.. 0-2302 



.. 1-2474 



Sulphydric " 



0-2423 



.. 0-2880 



.. 1-1912 



Ammonia 



(gas) 



0-5080 



.. 0-2994 



.. 0-5894 



Protocarburet of hydrogen . . 



0-5929 



.. 0-3277 



.. 0-5527 



Bicarburet of hydrogen 



0-3694 



.. 0-3572 



.. 0-9072 



Vapour of water 



0-4750 



.. 0.2950 



.. 0.0210 



tt 



Alcohol .. 



0-4513 



.. 0-7171 



.. 1-5890 



u 



Ether 



0-4810 



.. 1-2200 



.. 2-5563 



it 



Chlorhydric ether 



0-2737 



.. 0-6117 



.. 2-2350 



it 



Bromhydric " . . 



0-1816 



.. 0-0777 



.. 3-7316 



ft 



Sulphydric " . . 



0-4005 



.. 1-2508 



.. 3-1380 



tt 



Cyanhydric " . . 



0-4255 



.. 0-8293 



.. 1.9021 



tt 



Chloroform 



0-1568 



.. 0-8310 



.. 5-30 



H 



Dutch liquid 



0-2293 



.. 0.7911 



.. 3-45 



tt 



Acetic ether 



0-4008 



.. 1.2184 



.. 3-04 



u 



Acetone 



0-4125 



.. 0-8341 



.. 2022 



If 



Benzine 



0-3754 



.. 1-0114 



.. 2-6943 



ft 



Essence of turpentine 0-5061 



.. 2-3770 



.. 4-6978 



ft 



Chloride, of phospho's 0-1346 



.. 0-6386 



.. 4-7445 



ft 



Arsenic 



0.1122 



.. 0-7013 



.. 6-2510 



tt 



Silicium 



0-1329 



.. 0-7788 



.. 5-86 



tt 



Tin 



0-0939 



.. 0-8639 



.. 9-2 



tt 



Titanium 



0-1263 



.. 0-8634 



.. 6-836 



The specific heat which I have determined for the vapour of 

 water, by a great number of experiments, is 0-475; it is only 

 about one-half of that found by De la Roche and Berard. It 

 is very remarkable, that the specific heat of the vapour of water 

 is very nearly equal to that of ice, or solid water, and only one- 

 half of that of liquid water. 



Researches on the Developement of the "Viviparous Aphides. 

 By Dr. W. J- Burnett. 



" With every inquiring mind there is a deep interest connected 

 with the developement of animal life. To watch the origin and 

 rise of new forms, to trace the successive phases through which 

 they pass, as the ideas on which they are formed become more 

 and more definitely expressed, until finally they have their full 

 incarnation in perfect animals ; these, from the earliest times, have 

 been favorite studies with some of the most genial minds, and 

 over which they were accustomed to dwell with the profoundest 

 delight. 



" With a subject naturally so enticing, it is not surprising that 

 the Old Fathers of our science soon learned many of the more 

 general conditions which wait upon the introduction into life of 

 new' beings. In these studies, the class of insects has always been 

 quite prominent for the materials it furnished ; the commonness 

 of these animals, and the readiness with which they are at all 

 times obtained, render them easy objects of inquiry in all their 

 conditions of life, and there can be no doubt that many of these- 



