between the cells of the bark, and also between the bark and the wood : while no such separations are apparent when the leaf-buds are entirely inactive. These separations are various in size, and irregular in form ; their parietes consist of rows of cells, piled up one above another, like the bricks of a wall : and their cavities all communicate with one another. From these and other anatomical facts, which are given in detail by the author, he concludes that the propulsion of the sap along the vessels, resulting from the opera- tion of endosmose, will explain the descent of the cambium, which, being the nutritious portion of the vegetable fluids, corresponds in its nature to the chyle in animals.
March 23, 1843.
GEORGE RENNIE, Esq., V.P., in the Chair.
A paper was read, entitled, " Notice of an Extraordinary Lumi- nous Appearance seen in the Heavens on the 17th of March, 1843," in a Letter to S. H. Christie, Esq., Sec. R.S., by Sir John F. W. Herschel, Bart., F.R.S.
Collingwood, March 17, 1843.
My Dear Sir, — This evening, at half-past seven o'clock,! received notice from one of my servants of a luminous appearance in the sky, visible towards the S.W., which 1 immediately ran out to ob- serve, and which, as it differed in some remarkable particulars from any phenomenon of the kind I have ever before observed or seen described, I think it not unlikely to prove interesting to the Royal Society.
The evening was one of uncommon serenity and beauty : the moon, only thirty-eight hours after the full, having considerable south declination, was not yet risen. In consequence, the sun being already far enough below the horizon to leave only a faint glow of twilight in the west, the stars shone with unsubdued brilliancy, no cloud being visible in any quarter. Orion in particular was seen in all its splendour ; and commencing below that constellation, and stretch- ing obliquely westward and downwards, nearly, but not quite to the horizon, was seen the luminous appearance in question. Its general aspect v/as that of a perfectly straight, narrow band of con- siderably bright white cloud, thirty degrees in length, and about a degree and a quarter, or a degree and a half in breadth in the mid- dle of its length ; its brightness nearly uniform, except towards the ends, where it faded gradually, so that to define its exact termination at either end was difficult. However, by the best judgement I could form, it might be considered as terminating, to the eastward or fol- lowing side, at, or a very little beyond, the stars t, k, X Leporis, which stars (being of the fifth, or at most 5*4 magnitude) were pretty con- spicuously visible ; from which circumstance the degree of bright- ness of the ground of the sky in that region may be well estimated. Between these stars and fj. Leporis, the luminous band then com-
