1865.] Botany and "Vegetable Physiology. SI 



would be erroneous. It was consequently determined to undertake a 

 series of spirit levellings to fix the heights of the base lines, and verify 

 a certain number of principal stations, more particularly those situated 

 in the plains previously referred to. The main lines of levels were 

 executed by at least two persons, each furnished with a standard level 

 and pair of staves, one following the other, station by station, at a few 

 minutes' interval. The various sources of error, and the precautions 

 taken in order, as far as possible, to remove them, are detailed and 

 discussed. It is stated that a comparison between the results of the 

 spirit-levelling operations and those obtained from the principal trian- 

 gulation, is found to be highly satisfactory in all instances where the 

 vertical angles were measured at the time of minimum refraction, even 

 where the triangulations had been carried for long distances over the 

 plains already noticed. The average difference obtained at the end of 

 four circuits, averaging 550 miles in length is 3*06 feet, and the maxi- 

 mum difference at any station is 8*7 feet, which occurs at a station in 

 the valley of the Indus, 200 miles from the nearest hill station. In 

 combining the trigonometrical with the levelled values, the latter are 

 assumed to be correct and final ; and stations obtained by the former 

 process alone are referred to the nearest station of the line of levels. 



Sir John Herschel has proposed to the President of the Society 

 that an eyepiece for viewing the sun should be constructed, in which 

 the eye woidd be defended by a revolving metal plate, having in it two 

 very narrow slits diametrically opposite, each occupying a sector of 

 the disc, say half a degree. The diaphragm being made to revolve 

 five times in a second, a glimpse would be caught at intervals of one- 

 tenth of a second which suffices for contimxous vision. But the 

 quantity of light which would enter the eye would be only l-360th 

 part of the total light of the sun. If the disc were an annulus of 

 ten inches diameter, and the slits, four in number, were each l-100th 

 of an inch in breadth, the annulus revolving once in 2-5ths of a 

 second, the quantity of light would be reduced to l-785th part ; and 

 if the surface of the annulus next the sun were of polished metal or 

 looking glass, the annulus itself would not become very hot. The 

 annulus and the apparatus setting it in motion might be disconnected 

 with the telescope, so as not to communicate tremors. 



III. BOTANY; INCLUDING VEGETABLE PHYSIOLOGY 

 AND MICROSCOPIC BOTANY. 



Teteapanax papyriferum, the rice paper plant, appears to suit the 

 climate of New South Wales. M. S^vinhoe gives an account of it in 

 the ' Pharmaceutical Journal,' and describes the process of the prepa- 

 ration of the paper as follows : — 



The cellular tissue or pith attains its full size the first year. The 

 trunks and branches are mostly procured from the aborigines of the 

 inner mountains, in barter for Chinese produce ; they are rarely 



VOL. II. g 



