not long exist after respiration ceases, because the blood then no longer undergoes the necessary change in the lungs ; but we still find them for some time remaining in every part of the system; and, if respiration be artificially supported, imperfectly as it is in our power to effect this, we can perceive unequivocal proofs of the continuance of all the functions of the nervous, as well as muscular power, except of course that it can no longer, impress the sensorium, nor receive impressions from it where no sensorium exists*. It gives evidence of its power still to convey impressions along the nerves, however, by its still conveying those which excite the muscles.

Such is the foundation for the division which I have adopted of the functions of the animal body into sensorial, nervous, and 'muscular; and unless the facts here referred to can be controverted, I cannot perceive how it is possible to deny, that each of these classes of functions is supported by a power which may exist separately, and consequently can have no direct dependence on the powers which support the others.

It appears from what has been said, that the circumstances which form the line of distinction between the sensorial and nervous functions may be referred to three heads: 1st, The latter still continuing in the newly dead animal. 2d, Their being such as either evidently are, or may be, the effects of a chemical agent, while the sensorial functions have nothing in common with the effects of such an agent; and lastly, the sensorial power being subject to intervals of inactivity in the healthy animal, while the vigour of the nervous power is permanent. It is true, that two of the functions of this power have intervals of rest, namely, those of conveying impressions to and from the sensorium, and of exciting the muscles; but they only suffer these intervals, because they are operations of the sensorial and nervous powers jointly, and consequently fail when either of these powers fails. Those nervous functions which depend on the ganglian system, the formation of the secreted fluids, and the evolution

* Exper. 61, 62, 63, 64, 65, 66, 67, 68, 69.

of caloric, and are independent of the sensorial power, are permanent +.

The greatest difficulty, perhaps, to be encountered in defending the identity of the nervous influence and galvanism, arises from the former having been very generally regarded as part of the sensorial power. If the nervous power is once admitted to be merely a chemical agent, the question assumes a very different character. It has not been unusual to regard the sensorium as pervading, by means of the nerves, the whole system, and to suppose that we actually feel in the parts to which we refer our sensations. But a moment's reflection shews the inaccuracy of such a position. It is evident, that either this must be the case, or that there must be some centrical part to which the power of sensation is confined, and to which all impressions causing it are conveyed, a knowledge of the relative position of the part impressed being the result of experience. By disproving either of these positions, therefore, the other is established. Various ways present themselves of disproving the first. I shall confine myself to one, because it appears to be conclusive. When we complain of the toes of a limb which has been amputated, the cause of sensation cannot be in the toes. Here we see irritation of the stump of the nerve producing the same effect on the sensorium, which used to arise from irritation of its extremities. Many similar instances might be mentioned. We cannot shew why the immediate cause of sensation should so exist in these cases, and not in all. The sentient organ, therefore, is confined to a centre, to which all impressions, causing sensation are conveyed. It is thus that infants cannot distinguish the parts of the body impressed. This power is derived from experience, but, as the experience from which we derive it commences with our existence, and it is of no importance to us by what means we acquire it, it is a necessary consequence that we should wholly overlook the means of its acquisition; as, for example, we judge of distance by the eye, without thinking of the means by which we have been enabled to do so, and at first can hardly believe that they are such, as on inquiry we find them to be.

* See Part II. Chapter 9, on the use of the Ganglions. + Ib.

ART. VI. View of the Progress of Astronomy in Germany, for 1818. Extracted from Lindenau's Journal.

i. JANUARY and FEBRUARY, 1818.

I. Laplace on the Application of the Theory of Probabilities to
Geodetical Operations.

From the Annales de Chimie.

II. Littrow on Observations with the Transit Instrument. Taking the instrument of Königsberg, as employed by Bessel, for a favourable specimen, Professor Littrow examines the mean error of a great number of observations of transits of a star, and he infers that the mean error of a single observation was about ",12 in time, the most probable error ",10; the most probable error of the mean of the observations on three wires ",058; with five wires, the most probable error would have been ",045; and with seven ",038. He infers that it is perfectly right to carry our calculations, in general, to hundredths of seconds of time; but that we cannot be sure even of tenths of seconds of space, unless we employ as many as 200 wires; and that we may, in almost all cases, be satisfied with calculating to a single second, when space is concerned, without adverting to its fractions.

For determining the rate of a clock within half a second of space, it appears that 15 pairs of stars must be observed on two successive days, the most probable error of a single observation of this kind being ",13 in time.

The difference of two right ascensions of stars is also ascertained by a single observation within ",13 as the most probable error: so that to obtain the precision of ",01 in time, we require about 170 observations. The clock, however, does not appear to have been remarkably good.

For the immediate right ascensions, or the accuracy of the setting of the clock, the most probable error of 275 observations was,"18 in time; so that for a second of space we should require at least a comparison of 7 observations, and more than 100, to be tolerably certain within "1; consequently, the em

ployment of fractions of seconds must, in this case, also be commonly superfluous.

The author observes that in a former essay he had found the most probable error of Carlini's circle, or of the three foot multiplying circles of Milan and Ofen, equal to ",75, which is only 38 of that of the determination of the right ascension by a transit: and even the more imperfect circle of Königsberg, without being turned round, affords a precision about one-third greater than that of the right ascensions.

III. Bessel on the Influence of the Changes in the Earth's Substance upon the Latitudes of Places,

Demonstrates that no human operations can produce a sensible alteration in the conditions of the earth's rotation.

Mr. Laplace has more lately advanced the ingenious observation, that any material diminution of the mean temperature of the earth's substance might have been detected by the diminution of the length of the day: and we shall find, on computation, that a single degree of Fahrenheit might make an alteration of nearly a second in the diurnal period of rotation, and four or five minutes in the length of the year.

IV. Bohnenberger on the Adjustment of Astronomical Circles. By means of two objects at opposite points of the horizon, with some other expedients of a similar nature.

V. Muffling's History of the Measurement of the Rhine. With remarks on the best modes of executing maps.

VI. Hagen's Calculation of Observations of the Solar Eclipse of November 1816.

Finds about 9' 22",46 for the difference of longitude of Blackheath and Paris, according to Mr. Groombridge's observation of this eclipse, which, however, does not agree remarkably well with others. At the end of the paper we have the formulas employed by Bohnenberger in the calculation of eclipses, and some very convenient tables of Professor Bessel, corrected and enlarged.

VII. Littrow on the Motion of the Earth round its Centre of

Gravity.

This interesting paper is intended as a specimen of a simplification of some of the calculations in the Mécanique céleste, which Professor Littrow has already extended to the second and fifth books of that elaborate work; and which all true lovers of mathematical science will be anxious for his continuing and making public with as little delay as possible.

VIII. Buzengeiger on the Methods employed by the Greek Geometers in the Extraction of Roots.

Principally from Archimedes and Theon after Commandine.

IX. Littrow's Contributions to the Geography of Hungary.

From observations of Bogdanich, in his last illness, not agreeing well with each other.

X. David on Negative Refraction in the Neighbourhood of the Earth.

The observations were made at Prague, but they merely show some irregularities in the refractions of the sun's rays, at considerable altitudes.

XI. Extracts from Zach's Letters.

The first relates to records of eclipses, and the errors of ephemerides; the second to the family of Bonaparte.

XII. Extract of a Letter from Professor Littrow.

On the accuracy of the circle used by Bessel.

XIII. Zach on two Comets observed by Pons.

Their places somewhat loosely determined with moderate instruments.

XIV. Extract of a Letter from Dr. Olbers.

Containing observations, and the elements of one of Pons's

comets.