period 24h. 37m. 23-73s., in place of the period 24h. 37m. 27.745s., first obtained.

v

Mr. Cayley gives an expression for the angular distance of two planets, the sun being the centre of reference. Those who are interested in questions of this sort, will be able to judge of the nature of the paper from the statement that, and being the longitudes of the two planets in their orbits, and the longitudes of their nodes, and and their inclinations, then Mr. Cayley finds an expression for the required angular distance, in terms of cos (-), sin (u-v'), cos (u+v'), and sin (+ v'), the coefficients involving the quantities, e', o, and '.

Mr. Gill supplies a note on the Trapezium of Orion. He was able, with a good achromatic only 33 inches in aperture, to detect the exceedingly minute star 7 of the Trapezium. He also suspected the presence of a more minute star similar in R. A. to 9, and having the same declination as 8. It may be noticed in passing, that 6 of the Trapezium has been seen, with an achromatic only 31 inches in aperture, by Cooke.

It appears that, after all, the variable T Coronæ, whose sudden appearance so startled the astronomical world in May, 1866, may have been visible before evening set in, in England, on May 12th. For Mr. Walter, surgeon of H.M.'s 4th Regiment, in North India, saw the star shining at least as brightly as Alphecca at eight o'clock on the evening of that day, an hour corresponding to about halfpast two in the afternoon at Greenwich. It seems possible therefore that Mr. Stone was mistaken in rejecting the evidence given by Mr. Barker, of Canada; evidence, however, which we are bound to say bore a very questionable appearance.

Mr. Weston supplies a paper on the appearance of Jupiter's satellites and their shadows when transiting Jupiter's disc, on the evening of August 21st, 1867. He records the apparition of false satellites adjacent to the true ones, and distinct from the shadows. Such appearances, which have been observed by others, must, we think, be referred to optical delusion, since Mr. Dawes and other observers of the first class have failed to notice them. Mr. Weston, using a 9-inch Newtonian reflector, noticed that the shadow of the third satellite seemed larger than that of the fourth, an appearance which—as we have already said-seems to have been presented in almost every case, to observers who used reflecting telescopes.

Mr. Leeson Prince, in a paper on the same phenomenon, calls attention to the fact that the remarkable darkness sometimes observed in the fourth satellite when transiting Jupiter's disc, was observed and recorded nearly a century-and-a-half ago by Mr. J. Pound. This well-known astronomer took the satellite for its shadow, so dark was the former; and was surprised-soon after seeing the dark spot which he thus mistook-to see another and

darker shadow pass on to the planet's disc. The first, when in the middle of the disc, was almost as dark as the second when near the edge of the limb, but somewhat less in size. "From which it is very plain," he adds, "that the first of these spots was the fourth satellite itself, and the second its shadow. We have seen the first and second satellites appearing, not as dark spots, but as bright ones (somewhat differing from the light of Jupiter), for some little time after they have entered the disc; but as they approach the middle we lose sight of them; and we have frequently observed that the same satellites appeared brighter at some times than at others; and that when one of them hath shined with its utmost splendour, the light of another hath been considerably diminished. From whence it is very probable, at least, not only that the satellites revolve upon their proper axis, but also that some parts of their surfaces do very faintly-if at all-reflect the solar rays to us," an interesting passage, considering the date of the observation.

4. BOTANY AND VEGETABLE PHYSIOLOGY.

AMERICA.-Vibrios in Hot-water. Dr. Jeffries Wyman has been making some experiments on the appearance in hot-water of living organisms, which have some interest as touching upon spontaneous generation and some problems of Cryptogamic Botany. He concludes

1. In thermal waters, plants belonging to the lower kinds of algæ live in water, the temperature of which, in some instances, rises as high as 208° F.

2. Solutions of organic matter boiled for twenty-five minutes, and exposed only to air which had passed through iron tubes heated to redness, became the seat of infusorial life.

3. Similar solutions contained in flasks hermetically sealed, and then immersed in boiling water for periods varying from a few minutes to four hours, also became the seat of infusorial life. infusoria were chiefly Vibrios, Bacteriums, and Monads.

The

4. No ciliated infusoria, unless Monads are such, appeared in

the experiments referred to in the above conclusions.

5. No infusoria of any kind appeared if the boiling was prolonged beyond a period of five hours.

6. Infusoria having the faculty of locomotion, lost this when exposed in water to a temperature of from 120° to 134° F.

7. If Vibrios, Bacteriums, and Monads are added to a clear and limpid organic solution, this becomes turbid from their multiplication in from one to two days. If, however, they have been previ

ously boiled, the solution does not become turbid until from one to two days later.

The experiments of Dr. Child, of Oxford, and of other recent observers, are referred to by Dr. Wyman.

ENGLAND.-A new Arctic Conifer. In the Journal of Botany,' Mr. Andrew Murray describes the most northerly tree that has been met with on the north-west coast of America. It was found in the voyage of H.M.S. 'Herald,' forming forests on the banks of the rivers Noatak and Buckland, on the American side of Behring's Straits. This latitude is nearly seven degrees farther north than the limits of the woods on the eastern side of the American continent. This tree was described originally by Dr. Seeman as a variety of Abies alba, but Mr. Murray thinks that certain differences in the bract of the scale warrant a separation, and calls the new species Abies arctica. The desolate country where this tree is found is thus described by Dr. Seeman :-"There_is_nothing to relieve the monotony of the steppes. A few stunted Coniferous and Willow trees afford little variety, and even these, on passing the boundary of the frigid zone, are either transformed into dwarf bushes or disappear altogether. About Norton Sound groves of White Spruce trees and Salix speciosa are frequent; northwards they become less abundant, till in latitude 66° 44′ north, on the banks of the Noatak, Pinus alba disappears."

An Edible Fungus from Tahiti.-Mr. Brander, of Tahiti, gives an account of a fungus which is largely exported to Sydney. It is found principally in the Society and Leeward Islands, on decayed trees. The Tahitians call it "Teria iore" (i.e. "rat's ear"), from a fanciful resemblance of shape. The fungus first began to be collected in 1863, and fetches in China, where it is much esteemed and made into soups, from eighteen to twenty cents a pound.

Excellent articles (chiefly technical) occur in the same number of the Journal of Botany,' on the Plants cultivated or naturalized in the valley of Caracas, and on the staple products of Jamaica.

Weeds and their Characteristics.-Dr. Henry Trimen has made some very sensible remarks on the use of the term "weed," in reply to some observations on the same point by Dr. Seeman. Dr. Seeman says that a weed signifies a naturalized herb, which has a soft and membranaceous look, grows fast, propagates its kind with great rapidity, and spreads to the prejudice of endemic or cultivated plants, in places in some way or other disturbed by the agency of man. Dr. Trimen urges that the popular idea of a weed is any plant, irrespective of origin or appearance, occurring in cultivated ground, in addition to, and therefore more or less interfering with and injurious to the crop intended to be grown. This is the idea of a weed in the mind of horticulturists and farmers, and as it is sufficiently definite Dr. Trimen objects to the restricted sense

given by Dr. Seeman. The essential thing about a weed is, that it is out of place. A sunflower in a field of turnips is as much a weed as Brassica napus in a flower-garden, but reverse their situations, and the term is inapplicable to either. So when waste land, such as a heath, is enclosed and brought under cultivation, the species composing its original flora become weeds in the new fields. With regard to the term weedy" Dr. Trimen thinks that it means something more than "soft and membranaceous," many weeds being quite the reverse of this. From the situation of many "weeds" in rich and manured soil, and amongst other and taller plants, they acquire a luxuriant and rapid growth and a straggling habit. It is these characters which are especially implied in the term according to the old proverb, "Ill weeds grow apace." Etymologically no doubt, as Dr. Trimen and others before him have remarked, "weed' is connected with the Anglo-Saxon "weód," which means clothing or covering either of earth or man. Hence our expression "widow's weeds."

Fungi and Gregarines in the Hair.-A somewhat acrimonious correspondence on the chignon parasite has been going on in the 'Jourual of Botany' between Dr. Beigel and Dr. Tilbury Fox. After the occurrence of small organic growths on prepared hair had attracted public attention, Dr. Beigel appears to have obtained specimens of the parasite, and sent them to the distinguished German algologists, Rabenhorst and Küchenmeister. These gentlemen named the little plant-which is the simplest possible aggregation of highly refracting minute cells-Pleurococcus Beigelii-and Dr. Beigel related what they had done in the Journal of Botany.' Dr. Tilbury Fox, who is known as an observer and writer of great ability on skin diseases, published his opinion that the specific or even generic distinction of the parasite could not be maintained, and that like other fungoid growths, it was a function of the nidus rather than of the spore from which it sprang. The consequence has been a reiteration of the distinctiveness of his Pleurococcus by Dr. Beigel. The term Gregarine was unfortunately made use of by Lindemann, originally, in speaking of this growth; it is really, as admitted both by Drs. Fox and Beigel, most inappropriate Gregarine being indubitably animals, and of endo-parasitic habit.

Mr. John Bishop has described another case of Fungoid disease affecting the hair, to the Edinburgh Botanical Society. This occurred in the hair of the beard which, under its influence, broke off short, curling up and assuming a dried-up appearance as though singed. It appeared to be almost impossible to extirpate the fungus. Examination with the microscope showed a cellular fungus-growth within the hair-causing the destruction of the part by disrupting it from within. Sporules and mycelium branching among the broken fibres of the hair are occasionally to be seen.

Gases in Plants.-Messrs. Faivre and Dupré have experimented on this subject and submitted their results to the Edinburgh Botanical Society. They examined more especially the mulberry and the vine, and have arrived at the following conclusions:-1. The presence of gases in the interior of the root, stem, and branches in the mulberry and vine is a normal and constant fact. 2. The composition of these gases changes with the epochs of vegetation. 3. During the period of inactivity, carbonic acid is in very small proportion, and is scarcely appreciable. Oxygen is present to the same extent as in atmospheric air. During the phase of activity the contrary takes place, and the changes are more marked in proportion as the vegetation is more energetic; with the progress of vegetation, the proportion of oxygen diminishes. 4. In the roots during the epoch of vegetation, the quantity of oxygen is not so great, while that of carbonic acid is greater than in the branches examined under the same circumstances. 5. In the branches, as well as in the roots, there is an inverse relation between the oxygen and the carbonic acid; by adding to the normal oxygen that disengaged under the form of carbonic acid, we obtain a number which is scarcely above the proportion of oxygen in the air. 6. In the mulberry and vine, injections do not penetrate the pith or the bark, whether in the branches or roots. The ligneous layers are alone permeable to mercury. The more the formation of the vessels increases, the easier and more complete are the injections. The injections are fuller in the roots than in the branches; they are also more in the branches than in the young herbaceous shoots. In the old stems of the mulberry, the central layers cease to be permeable. 7. Microscopic examination proves that the injection specially penetrates the pitted and reticulated vessels, and also the spiral vessels in the young herbaceous shoots. 8. The pitted vessels show distinctly the mercury in the areolæ, as if in so many little pouches formed by thin portions of the wall; the same observations have been made in regard to the reticulated vessels.

FRANCE.-Absorption by the Roots of Plants. It is still a vexed question as to how far the roots, of plants absorb certain elements of their food, such as carbonic acid. M. Corenwinder has applied himself to the solution of this problem, believing that very rash statements as to the functions of the roots have been lately made by M. Boussingault and others. He states it as his conviction that plants have not the power of absorbing carbonic acid from the soil by their roots, or that at least the quantity which permeates the tissues from this source represents but a very small proportion of the total amount of carbon their tissues contain. Boussingault stated that in the air contained in an ordinary soil he found no less than ten per cent. of carbonic acid. M. Corenwinder asks what is the source of this large quantity of gas, and replies that it arises from the mass of decom