26o 



NATURE 



[JULY 1 6, 



the star through the middle of the ring or bar. This supposi- 

 tion, however, is shown to be erroneous. For stars of a less 

 magnitude than 5*5 there is always a detention in the apparent 

 time of emersion, which increases with the faintness of the stars 

 observed. The cause of the error, therefore, is physiological, 

 and due to the occulting micrometers employed. The law regu- 

 lating it having been found, the necessary corrections have been 

 applied to the measures, thus rendering the work of greater 

 use. 



The memoir represents the work of a business man over a 

 period of twenty years, and with an instrument having an aper- 

 ture of 3i inches. It contains much of interest, and will doubt- 

 less be appreciated as an important contribution to the know- 

 ledge of the stars in a cluster which is certainly one of the 

 grandest of telescopic objects. 



ON THE VEGETATION OF TIBET. 



TN the May number of the Journal de Botanique MM. Bureau 

 and Franchet describe a number of new plants from the col- 

 lections recently brought home by M, Bonvalot and Prince 

 Henry of Orleans, and give a general summary of their character, 

 of which the following is an abstract : — 



The collection was made almost entirely in a narrow band of 

 territory reaching from Lhassa eastward near the 30th parallel 

 ■of north latitude by way of Batang and Sitang to Tatsienlow, in 

 the province of Szechwan, in West China, from which place 

 their route was deflected at a right angle to Yunnan, 



Considered in its general aspect, the flora of this region, as 

 shown in the collection, is marked by the stunted form of the 

 shrubs and dwarf character of the herbaceous vegetation. Of 

 the forest trees, Coniferse and others, no specimens were 

 brought. It is characteristically a vegetation of high peaks, 

 ■where drought and strong winds are the main climatic features. 

 The Papaveraceaj are represented especially by dwarf, large- 

 flowered kinds of Meconopsis. The greater number of the 

 species oi Corydalis are not more than two or three inches high. 

 The Cruciferas, such as Parrya ciliaris, in the same way are 

 dwarf and large-flowered. Silene ccespUosa may be compared 

 with the most dwarf states of S. acaulis of our own high moun- 

 tains. The honeysuckle of Tibet constitutes only a small bush 

 about a foot high, with intertangled branches. But it is 

 especially in the Rhododendrons and Primulas that this dwarf 

 character is remarkable. All the Rhododendrons and Primulas 

 found between Lhassa and Sitang — H. principis, R. primula- 

 florum, R. nigra pundatum, Primula leptopoda, P. diantha, and 

 P. Henrici may be ranged amongst the dwarfest types of the 

 genera to which they belong. It is the same with Incarvillea. 

 The Tibetan species belong to a group found also in Kansu and 

 ■Central Yunnan, with stem almost obliterated and corolla very 

 large. 



Passing eastward in Szechwan the flora puts on a different 

 character. The leaves become larger, the number of flowers 

 to each plant increases. There are many Rosacese, Orchids, 

 and species of Pedicularis ; amongst the Compositie the genus 

 Senecio is particularly well represented, and there are several 

 Everlastings that approach the Edelweiss of the Swiss Alps. 



The flora af this eastern part of Tibet and western region of 

 Szechwan has a strong affinity both with that of the Sikkim 

 Himalaya and that of Central Yunnan. Meconopsis Henrici 

 ■represents the Himalayan M. simplicifolia. Hook, et Thorns. ; 

 Astragalus litargensis, A. acaulis, Benth., Rubus xanthocarpus, 

 -R. sikkimensis ; Brachyactis chinensis, B. menthodora : Gnapha- 

 lium corymbosum answers to G. nubigenum ; Androsace bisulca 

 to A. microphylla ; and there are many other similar parallels 

 between the plants of Tibet and Sikkim, and in the same many 

 parallels may be found between the new species found by our 

 travellers in Tibet and those gathered by Delavay in Yunnan. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Society, June 18.— "An Apparatus for testing the 



Sensitiveness of Safety-lamps." By Frank Clowes, D.Sc. 



Lond., Professor of Chemistry, University College, Nottingham. 



Communicated by Prof. Armstrong, F.R.S. 



The following apparatus has been devised to render easy the 

 NO. II 33, VOL. 44] 



process of testing the sensitiveness of different forms of safety- 

 lamps when used for detecting firedamp. To enable satisfactory 

 tests to be made in the laboratory, it was necessary to insure 

 (l) the easy and rapid production of mixtures of firedamp and 

 air in known proportions ; (2) to insure economy of the 

 artificially prepared methane, which represented firedamp ; and 

 (3) to examine the flame of the lamp under conditions as 

 satisfactory as those existing in the mine. 



A wooden cubical box of about 100 litres capacity was 

 constructed so as to be as nearly gas-tight as possible. It was 

 then made absolutely gas-tight by painting it over with melted 

 paraffin wax, which was afterwards caused to penetrate more 

 perfectly by passing an ordinary hot flat-iron over the surface. 



This testing chamber was furnished with a small inlet tube at 

 the top, and with a similar outlet tube below. It had a plate- 

 glass window in front for observing the lamp in the interior, and 

 a flanged opening below for introducing the safety-lamp. This 

 opening was closed by a water-seal consisting of a small zinc 

 tray supported by buttons, and containing about 2 inches depth 

 of water, into which the flange dipped. A mixer was arranged, 

 which consisted of a light flat board, nearly equal in dimensions 

 to the section of the chamber, and suspended by an axis from 

 the upper corner of the chamber. The mixer was moved 

 rapidly backwards and forwards from the side to the top of the 

 interior of the chamber, by grasping a handle projecting through 

 the front of the chamber. 



When a mixture of air with a certain definite precentage of 



