122 



HARDWICKE'S SCIENCE-GOSSIP. 



distribution of electricity over the surface of the earth 

 and in the atmosphere. M. Peltier states that sea- 

 water is invariably charged positively, and all ex- 

 periments (with exception of one veiy doubtful one) 

 go to show that the surface of the earth is invari- 

 ably negatively charged. It is known, too, that the 

 atmosphere is charged positively when the sky is 

 serene, and no disturbance of its condition produced 

 by clouds, storms, fogs, &c. The natural supposition 

 is that the positive electricity in it is produced by 

 the vapour rising from the sea. 



M. Quetelet states that the existence of electricity 

 in the air begins to be manifested at a distance from 

 the surface of the earth from one to ten yards, accord- 

 ing to the place of observation, and, the higher we 

 rise, the greater is its intensity, though in the same 

 horizontal plane we get diurnal maxima and minima 

 as well as monthly variations. Though we consider 

 the earth for a few miles around us at zero potential, 

 yet we find by connecting two points on its surface 

 some distance apart by a conductor that a trans- 

 ference of electricity from one point to the other 

 ensues, thereby showing that at different points of 

 the earth's surface, the intensity of its negative charge 

 varies, sometimes even to the extent of hundreds of 

 "volts." 



Thus the distribution of atmospheric electricity is 

 analogous to the distribution over a Leyden jar, the 

 earth's crust being the inner armature, its negative 

 charge being held on its surface by the positive 

 charge of the atmosphere, forming the outer arma- 

 ture, the lower part of which acts as the dielectric. 



When, however, clouds arise we have a disturbance 

 of the normal electrical state of the air, and manifes- 

 tations of negative electricity occur. These may be 

 due to clouds, similarly charged by being formed 

 near the earth, or of vapours rising from the surface. 

 M. Quetelet, however, denies the formation of 

 negatively charged clouds, and attributes these mani- 

 festations solely to the induction produced on a 

 neighbouring cloud by one more strongly charged 

 with positive electricity. 



" We must not," says De la Rive, " think that a 

 cloud is in electric properties analogous to a metallic 

 conductor where the electricity only is superficial, 

 but as an agglomeration of distinct electrified globules 

 of water which preserve their individual electricity, 

 beforehand distributed among the particles of vapour 

 of which each globule is formed. Thus in order 

 to understand the electrical phenomena of clouds, 

 it is necessaiy to be familiarised with the idea of 

 individualities of each of the composing globules ; 

 many globules form a flake ; many flakes form a 

 ' mamilla ; ' many ' mamillje ' a cloudlet ; many 

 cloudlets a cumulus ; many cumuli a nimbus. Thus 

 each has its own peculiar and independent electric 

 sphere in equilibrium of reaction between them- 

 selves and with the general exterior sphere of the 

 cloud." 



This theory explains very well certain phenomena 

 connected with thunder, on which limited space for- 

 bids me to dwell, and bearing it in mind, we shall 

 be able to understand two of the principal forms of 



lightning. 



(7l> be continued.) 



BOTANICAL NOTES FBOM THE SWISS 

 HIGHLANDS. 



V. Mount Pilatus. 

 By Dr. De Crespigny. 



{Continued frojii page 107.] 



EXCURSION from hotel to the " Tomlishorn,"— 

 7300 — highest point, five miles there and back, 

 along a safe but giddy path ; here and on the adjoin- 

 ing crag : Arenaria saxatilis. Gnaphalhnn leontopo- 

 dium, but rather scarce. The well-known edelweiss, 

 remarkable for the large woolly involucres of its 

 capitula, whole plant hoaiy and tomentose. Erigcron 

 uniJ?o?-iis differs but slightly from alpimts, florets 

 more rose-coloured than purple, involucres more 

 woolly than hairy. 



The path upwards to the " Oberhaupt," a toilsome 

 zigzag, over loose rocky debris, will require a good 

 steady pull of about three-quarters of an hour to 

 accomplish. Fine view — clouds permitting — on 

 emerging from the "chimney,"* somewhat similar 

 to that from the Tomlis ; good path onwards to the 

 upper inn and Esel. On the right a steep slope of 

 pasturage, left a rocky wall, affording glimpses here 

 and there of the awful precipices which overhang the 

 Nauen, and which are fully revealed on ascent of the 

 Esel — to be done in a ten-minutes' climb up steps 

 roughly hewn along the face of its outer escarp- 

 ment. Here, on the "band," on the upper pastur- 

 age, and on the rocks and debris by the mule path 

 downwards, the following good things (besides many 

 of the others already mentioned) may be looked for 

 with every probability of their being, most of them 

 at any rate, met with and consigned to the vasculum. 

 Arenaria ciliata, Esel. Ahine Villarsii, Esel. 

 Anetnone vernalis, radical leaves pinnate, involucre 

 silky ; alpina, radical leaves bi-tripinnate ; flowers 

 larger, petals in both species white, more or less 

 tinged with violet externally ; the former in seed ; of 

 the latter, the var. siilphiirca, petals yellowish, is not 

 uncommon. Arabis pumila, Esel, in fissures ; bclli- 

 difolia. Akhemilla pentaphylla. Atidrosace chamcB- 

 jasnte; Helvetica; (= b}y aides) Band, leaflets hairy, 

 densely imbricated ; flowers subsessile, solitary, ter- 

 minal. Allium Victorialis ; debris; stem bifoliate, 

 leaves sessile, flowers greenish-white ; the alpine 

 representative of ursinum. Avena distichophylla, 



* The " Kriesiloch " — a natural hollow in this overhanging 

 crag, thirty feet or more, high and perpendicular. It is now 

 ascended by means of a ladder ; formerly adventurous moun- 

 taineers had to climb it chimney-sweeper fashion— by their 

 knees and elbows. , J 



