observations, which throughout gave consistent results, was 0:37 of a degree. To compare this effect with that from a terrestrial source of heat, Prof. Smyth placed a Palmer's candle 14 ft. 9 in. from the pile, and took readings of the needle with the same alternations of exposure as he had adopted for the moon. Twenty-one readings gave a mean deflection of 0.77 degrees; so that the deduced heating influence of the moon appeared equal to half that shed by a candle to a distance of fifteen feet.

Professor Smyth did not ascertain what this would be in terms of a recognised scale; but M. Marié-Davy has since done so, using, however, not the mean of the two nights' observations, but that given by the first night's, and assuming that the heating power of the candle used by him was not sensibly different from that employed on Teneriffe. The first or full-moon night's deflection was 0-25 of a degree, or a third of the candleeffect. Marié-Davy's candle, at fifteen feet from his pile, gave a deflection to his needle amounting to 17.3 divisions. A third of this would be 5-8 divisions, and this (the scale value of his needle being known to M. Marié-Davy) answered to 0.00075 of a degree centigrade for the heating effect of the moon upon a body on the summit of Teneriffe.

-was

Passing over some negative results arrived at by Prof. Tyndall, in 1861,* from trials made upon the roof of the Royal Institution, without a condensing means beyond a large cone, and which were explained upon the hypothesis put forth by Buys Ballot, we next come to the experiments of the Earl of Rosse, for the making of which far superior means were available than any at the disposal of previous investigators. One of the famous Parsonstown reflectors the "three-foot equipped specially for the work. The difficulty of compensating for the effects of radiation on the anterior face of the pile compelled the adoption of two piles,† which were connected "in such a manner that a given amount of heat on the anterior face of one pile produced a deviation equal in amount and opposite in direction to that produced by an equal amount of heat on the anterior face of the other pile." Small concave mirrors were used to still further concentrate the lunar rays collected at the focus of the great mirror. The galvanometer was of the construction introduced by Prof. Thompson to meet the requirements of the delicate currents employed in sub-Atlantic telegraphy. Instead of the needle pointing to engraved degrees upon a circle beneath it, a mirror is attached to the suspending bar, and a lamp-flame is reflected from this upon a distant scale. In this manner, deflections imperceptible “Phil. Mag.” 4th ser. xxii. 377 and 470. † See Plate and description.

in the needle itself can be magnified to any extent by increasing the distance between the lamp and the scale. This form of instrument has been used by Mr. Stone for the purpose of measuring the extremely feeble heat radiated from the stars: it is possible that but for its capabilities these delicate experiments would never have been attempted.

Lord Rosse essayed to determine the proportions of moonheat coming from three sources: 1. That which it may be supposed the moon sheds in virtue of its being a globe possessing internal or cosmical heat. 2. That solar heat which is reflected from the surface with the reflected light. 3. That which, coming from the sun, is first absorbed at the lunar surface and then radiated as dark heat. The first and third qualities are such as we should expect to find but slightly manifested at the earth's surface by reason of the intercepting influence of the atmosphere. The second source is that from which we might expect the most marked results. Observations were made during the winter and spring of 1868-69, on sixteen nights in all, on some of which the moon was several days from full. At five days old it gave evidence of heating power; and the amount of deviation of the needle increased with the phase, showing that the law of variation of the moon's heat does not differ much from that of the moon's light. The maximum of one was found to be coincident in time with the maximum of the other; there was no evidence of greatest heat coming at the period of greatest insolation, which would be at about third quarter.

To test the proportion of light to dark heat in the rays reaching the mirror, the Earl of Rosse placed screens of plate glass before the pile on four nights near the time of full moon, and the result was a great interception of heat, manifested by a small deviation of the needle. About 8 per cent. was considered to be the probable amount that passed through the screens, from which Lord Rosse concludes that the greater part of the lunar heat is that which has first been absorbed by the moon's surface and then radiated from it.*

By computation in one case, and by observation of the relation of solar and lunar heat to that of a vessel of heated water in another case, the relation of solar to lunar radiation was found to be nearly as 80,000 to 1. And by the use of a blackened cistern of hot water, subtending the same angle at

This absorbed and radiated heat is presumably dark. How then did it get through the atmosphere? There would seem to be heat which passes through air, and yet is obstructed by glass. One result of thermoscopic investigations upon the light of moon and stars may be to improve our knowledge upon such points as this.

diameter instead of a lens, and with a modification of the double pile arrangement used by Lord Rosse. Only one pile was really used, but it was so mounted that both faces were similarly exposed to atmospheric influences. The results confirm Lord Rosse's conclusions that the moon has no cosmical or internal heat to give us; that the heat she does impart varies as the phase of illumination; and that the lunar is to the solar radiation as 1 to 80,000. Further than these, Marié-Davy infers that the diffusive power of the moon's surface is about the same as that of chromate of lead, as determined by MM. Desains and Provostaye, and that the moon's heat, by reason of its large proportion of obscure rays, is much more impressionable by atmospheric humidity than solar heat. He found that, with the moon at the same age, his measured heat in November was six times as great as in October. He ascribes this excess to the use of a mirror instead of a lens, and concludes that the latter absorbs six times as much lunar caloric as the former.t * "Comptes rendus," lxix. p. 1154.

DESCRIPTION OF PLATE LIV.

A A. Converging beam from great reflector.

B B. Small concave mirrors (fixed upon a bar screwed to the eye end of the telescope), one of them receiving the beam and condensing it upon the corresponding pile.

CC. The two piles, each composed of four pairs of bismuth and antimony plates; the faces exposed to the mirrors being laterally sheltered by metal cones, and their posterior faces covered with brass caps filled with water for maintenance of nearly uniform temperature.

DD. Wires leading to the galvanometer.

E. Reflecting galvanometer formed of a, a coil of fine wire surrounding b, a delicate magnetised needle covered by a small plane mirror, suspended by a filament of silk, and rendered partially astatic by the second small magnet c, rigidly connected with it. d is a large arched magnet sliding upon a vertical bar; its use is to adjust the zero of the needle and regulate its sensitive

ness.

F. Lamp. A beam from its flame passes through a hole in the board G and falls upon the mirror at b, thence being reflected on to a graduated scale on the opposite side of G. The displacement of the light-spot is a greatly magnified measure of the needle's deflection.

15

UNDER CHLOROFORM.

BY B. W. RICHARDSON, M.D., F.R.S.

I

HAVE taken as the text of one or two papers, the familiar title given above, not with the strict intention of confining what I have to say to the one subject, chloroform. But, accepting chloroform as a type of a number of chemical substances which possess the property of inducing sleep and insensibility, I propose rather to consider the general subject of sleep and insensibility as induced by artificial means. It will be my object to write so simple an account of the progress of discovery on the subject in hand, that the intelligent reader may easily follow me and may, in the end, feel himself in safe possession of all the more important truths which modern science has brought to light in relation to anæsthesia.

HISTORICAL NOTES.

The practice of destroying, or rather of suspending consciousness, for and during the performance of surgical operations, although it has been developed in our time, is as old as the practice of administering soothing remedies for the relief of pain in the course of disease. The reference to mandragora so often made in classical works of old, and in some of our earliest English poets, bears on the employment of an agent of this kind. Mandragora, or mandrake, belongs to the natural order of plants Solanaceae, and is of the same genus as the Atropa belladonna, deadly nightshade. The Atropa mandragora is a plant common to the Isles of Greece, and was used by the early Greek physicians as a sedative in various ways. The plant is said to be more determinate in its action than belladonna, and the odour is much more unpleasant. Very soon after the introduction of ether as an anæsthetic, Sir James Simpson pointed out that the mandrake had been recommended by Dioscorides for the specific purpose of making surgical art painless, and he quoted the passages in which the plan is described. "Some persons," says Dioscorides, "boil the

root of mandrake in wine down to a third part, and preserve the decoction, of which they administer a cyathus, about a fluid ounce and a half, in want of sleep and severe pains of any part, and also before operations with the knife, or the actual cautery, that they may not be felt." Speaking further on of a similar decoction which is diluted with wine, he says, "three cyathi of this wine are given to those who require to be cut or cauterised, when, being thrown into a deep sleep, they do not feel any pain."

The same author, Dioscorides, describes a kind of mandragora called morion; he records, that a drachm of it being taken as a draught, or eaten in a cake or other food, causes infatuation, and takes away the use of the reason. The person sleeps without sense, in the attitude in which he ate it, for three or four hours afterwards. Medical men also use it when they have to resort to cutting or burning.

Pliny, after Dioscorides, is more circumstantial still in respect to mandrake, teaching that the leaves are more potent than the root. The draught of its preparations may, he says, kill, and it has the power of causing sleep in those who take it. The dose is half a cyathus. It is taken against serpents and before cuttings and punctures, lest they be felt. And then he adds, very curiously in respect to the medicine, "for these purposes it is sufficient for some persons to have sought sleep from the smell." And yet another author, Apuleius, speaking of mandragora, says of it, "If any one eat of it he will immediately die, unless he be treated with butter and honey, and vomit quickly. More, if any one is to have a limb mutilated, burnt, or sawn, he may drink half an ounce with wine, and while he sleeps the member may be cut off without any pain or sense.'

I have followed, in relating these details, the very clear, able, and concise work of the late Dr. Snow.* The reader will probably agree with an observation he makes on the strangeness of the fact, that with such passages from such well-known authors in existence, the practice of preventing pain during surgical operations was entirely unknown just prior to the year 1846.

The fact is still more singular, when we find that through the middle ages, and through the period of the revival of letters, and down to the last century, notions of the practice of annulling pain before operations, and even experiences of the practice, were constantly cropping up. Snow, in the chapter of the work already cited, gives us several more instances of this kind. He quotes from the work entitled Koukin-i-tong, a general collection of ancient and modern medicines of the Chinese, that one Hoatho, a physician, who lived about the * See "Snow on Chloroform and other Anæsthetics." Edited by RichardChurchill and Sons, 1858. Historical Introduction, pp. 1–36.

son.