occasion, was one combining in a high degree simplicity with accuracy; and the quantities of gas. operated on, together with the great care to discover and avoid every possible source of error, have produced a most satisfactory coincidence in the general results of the numerous experiments here described.

In each of the ten first experiments, between three thousand and four thousand cubic inches of common air were respired in the space of from ten to eleven minutes each; and in all of them it was observed that the quantity of expired was less than that of inspired air, although, if the chemical effect of respiration is merely the acidification of carbon in the lungs, there ought to be no difference between the two quantities, as a cubic inch of oxygen gas produces precisely the same bulk of carbonic acid. From experiments in which a similar deficiency has appeared, it has been supposed by former enquirers that a portion of the oxygen or azot of the inspired air was actually absorbed : but in the ten experiments here alluded to the deficiency is upon the whole so small, and yet so variable, from to of the whole, that it is probably entirely accidental: and is in our. opinion well accounted for, by the following remark.

"The deficiency, in our opinion, principally arises from the difficulty in bringing the lungs precisely to the same state after, as before the experiment; and it must be recollected that the operator commenced by a forcible expiration into the open air, but finished by a forcible expiration into the mercurial gasometer. Now, although this gasometer was counterpoised by weights in the scale attached to it, yet we can easily conceive that more resistance might be afforded to the complete evacuation in the latter case than in the former, and consequently the lungs might contain a few inches more after the experiment than before it."

In the 11th experiment, 3460 cu

bic inches of air were respired in 11 minutes, and a deficiency of 23 inches was thereby incurred. The air previously to being breathed, consisted of 21 oxygen, and 79 azot, in 100 parts; but after respiration it consisted of 8. 5 carbonic acid, 12. 5 oxygen, and 79 azot.

In the 12th experiment an assistant was made to respire 3300 cubic inches of air, which, after passing through the lungs, were found to have encreased to 3311 inches: the time employed was only 5 minutes, but notwithstanding that in this case the respiration was twice as rapid as in the former one, the expired air contained as before, s. 5 per cent of carbonic acid,

In the 13th experiment, the same operator, who performed all the others except the 12th, respired 9890 inches in 24 min. 37 sec. The deficiency after the process amounted only to 18 inches; and the expired air was found to consist of 8 carbonic acid, 13 oxygen, and 79 azot.

In the 15th, experiment, 300 cubic inches of common air were breathed repeatedly till the operator nearly fainted; the residual gas on analysis was found to consist of 10 carbonic acid, 4 oxygen, and 86 azot, but its absolute quantity was not ascertained.

In the 16th experiment respiration was performed on gas obtained from oxymuriat of potash consisting of 97. 5 oxygen, and 2.5 azct. 3260 inches were respired in 9min. 20 sec. and there appeared a deficiency of 67 inches. The gas feriespiration consisted of 11 carbonic acid, 83 oxygen, and 6 azot.

Here it is plain that a greater quantity of carbonic acid was form ed from oxygen, than from commoa air, and the experimenters infer that one use of azot is to regulate the quantity of oxygen consumed in respiration. The additional quan tity of azot, which made its ap pearance in this, and the preceding

Z22

experiment is supposed to arise "From that portion still retained in the lungs, notwithstanding the forced expiration at the beginning of the experiment, and considering that in the 14th and 15th experiment, where the same air was repeatedly breathed, the proportion of azote was in the one case 85, and in the other 86 per cent. it seems fair to presume, that the residual air contained in the lungs after a forced expiration may amount in 100 parts, to not more than 16 oxygen, and 84 azote : any one who reflects upon the structure of the lungs, and the minute ramifications of the extremities of the bronchial vessels; and when he also considers that those parts of the lungs with which the air comes in contact, if spread out would present a surface equal to that of the superficies of the whole body; and lastly, that this viscus is so exceedingly spongy and porous, That when once inflated, it is ever after impossible by ordinary mechanical means to expel the air completely, he will easily perceive, not only that a large portion of air must remain for a considerable time in contact with the internal surface of the lungs, where it is liable to lose a portion of its oxygen, but also that the residual quantity of air in the lungs, after the most violent attempts at expiration, may be very considerable."

In order to prove the truth of this explanation, 3420 inches of gas of the same purity as that used in the former experiment, were respired and received successively into 13 different gazometers. The first portion was found to contain 25 per cent of azot, the second and third portions contained 10 per cent, and the last portion 5.5 per cent. The general average of the whole amount of azot was 6.5 per cent.

From the above facts the following conclusions may be drawn: Atmospheric air when subjected to a single inspiration, returns charged with from 8 to 8.5 per cent. of carbonic acid, nor by any number of subsequent inspirations does the a mount exceed 10 per cent.

When respiration is attended with distressing circumstances a portion of oxygen is probably absorbed.

There is no evolution of hydrogen or any other gas except carbonic acid during respiration; and from the quantity of carbonic acid generated exactly corresponding with that of the oxygen consumed, there does not appear to be any of this latter expended in the formation of water.

absorption of azot. There does not appear to be any

18, Description of an Apparatus for the Analysis of the compound inflẩmmable Gasses by their Combustion; with Experiments on the Gas from Coal, explaining its Application. By Wm. Henry, M. D.

The object of the apparatus here described is to enable the chemist to analyse the compound inflammable gasses by combustion with oxygen, instead of detonation; the former method being both more accurate in itself, and allowing a greater quantity of gas to be submitted to experiment. For the results of the experiments here related, we must refer to the original.

By

19. An Account of some Peculiarities in the anatomical Structure of the Wombat; with Observations on the female Organs of Generation. Everard Home, Esq. F. R. S. 21. Eclipses of the Satellites of Jupiter, observed by John Goldingham, Esq. &c. at Madras.

The discovery of the difference of longitude between two places by means of the satellites of Jupiter is supposed to be an easy process: but the remarks in this paper will point out many circumstances to be taken into consideration, which materially affect the attempt. For the circumstances at both places should be similar, and favourable: the telescopes should have equal powers, and both immersions and emersions should be observed. If the circumstances are favourable at one place, and not in another, very different results will be obtained. Tables are given of the eclipses of each satellite observed, with the circumstances at◄

tending them. The expression planet high, continually occurs. We wish that the height had been more accurately ascertained. It may indeed be discovered with sufficient ease by a person with a globe and

the nautical almanac before him, but a column assigned to the height would have been more satisfactory. This paper should be read by all young observers on the eclipses of Jupiter's moons.

IN his former volume Mr. Parkinson treated of thedifferent vegetable remains that have been discovered in a fossil state in the volume now before us he enters on the description of animal fossils, but proceeds no further than the Zoophytes, reserving the rest of his subject for a future volume. The genera here treated of are the Tubiporites, Madreporites, Alcyonia, Encrinites, and Pentacrinites, very few of which can be referred with any probability to those living species of Zoophytes with which we are hitherto acquainted.

The descriptions are full and well compacted, and display throughout that minute accuracy which can only be attained by a long and intimate acquaintance with the general subject and the individual specimens, and are accompanied by figures from original drawings so admirably executed as to leave all former graphical representations of these subjects far behind. But besides the reputation of an accurate describer, Mr. Parkinson merits the higher praise of an original discoverer, and he has satisfactorily solved one of the two great difficulties attending all theories with regard to the formation of fossils. That which he has not solved is the remarkable fact that though the hard parts of these Zoophytes in their live state are

for the most part composed of carbonat of lime and are fre quently also when fossil composed of this substance, yet there are numerous instances of fossil zoophytes compleatly penetrated by Aint, and what adds to the difficulty is that these silicified remains are generally found imbedded in limestone in which hardly an atom of silex is to be discovered. The second difficulty is to explain how the exquisitely minute organization of these animal fossils can be retained, at the same time that the process of petrification is compleat and the whole is apparently become a mere mineral body. This entire removal of animal matter however Mr. Parkinson has demonstrated in several instances to have been gratuitously assumed without proper examination; for on immersing specimens of calcareous fossil Zoophytes in very dilute muriatic acid, the earth was by degrees taken up, and there remained behind a fine membrane of animal matter which exhibited in some instances even the form and colour of the recent animal. With the silicified fossils the same method of analysis could not be resorted to, but there is a high analogical probability that in these, as in the others, there exists a cellular tissue of animal matter in the interstices of which only the silex is deposited.