*576 



SCIENCE. 



Science 

 riostti 

 in. 



On the Hjmmit of Ben-Nevis, about mid-day, the 

 thermometer, with wet bulb, stood at 36 5 Fahr. in 

 the cloud. The temperature soon after rose to 39, 

 and the cloud in which we stood was partly evaporat- 

 ed, partly 'borne away, leaving a view of the sublime 

 scenery by which we were surrounded. The dense 

 clouda on every side hung down like curtains around 

 the panorama, and their under margins were so de- 

 finite, and the atmosphere otherwise so clear, that one 

 felt disposed to stoop down as if to see farther into the 

 distant landscape, which was illuminated by the sun- 

 shine. The altitude of this magnificent accumula- 

 tion of vapour, was between 3000 and 4*000 feet above 

 the level of the sea. But it was far from uniform, at 

 least the profile of its under surface was alternately 

 elevated and depressed, so that at one time we saw 

 beneath it the mountains of Perthshire and the He- 

 brides ; and, in a few minutes after, our view was 

 confined to the valleys surrounding Ben-Nevis. Soon 

 after mid-day, the weather became more unsettled. 

 Sometimes a cloud rose suddenly on the face of the 

 mountain, and rolled down the valley. Sometimes 

 one came from the neighbouring summit of Corry- 

 Rignson, as if urged by a violent wind ; and at other 

 times the condensed vapour ascended rapidly in im- 

 .mense volumes from the centre of the valley below, 

 and was aptly compared by one of the party to the 

 smoke from a town on fire. The magnificence and 

 variety of these clouds amply compensated for the 

 loss of the terrestrial scenery. 



The summit of Ben-Nevis, for a considerable ex- 

 tent, was covered with snow. Not only was there a 

 ravine in the immense precipice on the north side of 

 that mountain, containing an upfilling of snow almost 

 entitled to the name of a glacier, and several beds of 

 great depth lying fully exposed to the sun ; but there 

 was a general covering of about three inches depth, 

 which had fallen since the same party was there two 

 days before. This was easy to be conceived, for 

 about one o'clock, the temperature fell to 33.5, a 

 fresh breeze having arisen from the south-east, bring- 

 ing a nimbus along with it. When the storm reach- 

 ed us, it proved to be snow, which continued to fall 

 very heavily for about two hours. Soon after it be- 

 gan, our attention was attracted by a very singular 

 noise, which was heard every where around us. It 

 exactly resembled the hissing sound which proceeds 

 from a point on an excited prime conductor, or a 

 strongly-charged Leyden phial of an electrical appa- 

 ratus, indicating the emission of a pencil of electric 

 light, which, had the daylight not overpowered it, 

 would certainly have been visible. This sound was 

 always loud, and more or less distinct for about an 

 hour and a half. It seemed to proceed from every 

 point near us. But amidst the general hissing, I was 

 convinced that I could specify the summit of my um- 

 brella and several points of the rocks from which I 

 heard it issuing. --On removing to the cairn on the 

 highest point of the mountain, the phenomenon be- 

 came remarkably manifest, and we could almost de- 

 termine the stones from which the pencils were pro- 

 ceeding. 



Though this sound of the electric fluid is so com- 

 pletely sui generis, as scarcely to be confounded with 

 anything else, an accident now occurred, which af- 

 forded another evidence of the nature of the action 

 which occasioned it, when we were seeking for none. 

 One of the party having fallen behind the rest, in ex- 



amining some parts of the mountain, came up to the 

 others while they were wondering at the sound, and Cur ! osltus 

 trying. to find shelter from the storm beside the cairn ; 

 and were it not, that complacency and fortitude are 

 unalterably expressed in his countenance, we should 

 certainly have concluded, either that he had seen " the, 

 angry spirit of the storm," or something else very ter- 

 rific ; for, as is always stated of persons having wit- 

 nessed such sights, " steterunt comic" the hair of his 

 head stood on end not indeed all his hair, but those 

 locks only which enjoyed something of their natural 

 freedom to move, having withstood the pelting action 

 of the snow and rain several hours. For botanists, 

 contrary to the practice of the vulgar, sometimes find 

 it more convenient to wear their caps in their pockets. 

 Several other gentlemen, then, by uncovering their 

 heads, gave their hair an opportunity of exhibiting the 

 beautiful phenomena of electrical attraction and re- 

 pulsion. 



ELECTRO-MAGNETISM. 



The new science of ELECTRO-MAGNETISM which has 

 been established since our articles ELECTRICITY and 

 MAGNETISM were printed, affords a series of most amus- 

 ing and interesting experiments. 



As we propose to give a full account of the whole 

 subject under the article THERMO-ELECTRICITY, it 

 would be unnecessary to anticipate any of the details 

 under the present article. 



HOROLOGY. 



1. An account of Brcguet's eye piece chronometer for 

 'counting fractional parts rfa second. 



In observing the disappearance of a star behind the 

 wires of a transit instrument, it is not easy to observe 

 to thejiflh part of a second of time ; but as this quan- 

 tity corresponds to three seconds of right ascension it 

 becomes a matter of considerable consequence to dis- 

 tinguish even tenths of a second. 



The instrument by which M. Breguet proposes to 

 supply this defect is shown in Plate CCCCLXXXV, 

 Fig. 6, where AB is a section of the eye piece of a 

 telescope through the anterior focus of the eye glass, 

 the field bar being represented by the black ring. 

 The box CD attached to it contains a chronometer 

 which points out on the dial plate EF, by means of the 

 index G, every ten seconds, the dial plate being divided 

 into ten minutes. Two other indices m n, revolve 

 through the field of the telescope, and in the plane of 

 the wires. The shorter one, n, marks units or single 

 seconds upon a segment of a circle o p of 60 divided 

 into ten seconds. The larger index, m, terminates in 

 an opaque disc, the centre of which describes in one 

 second a segment of 6'0, which may be divided into 

 ten parts or tenths of second?. The prolongations of 

 the divisions 1, 3, 5, 7, 9, determine the distances of 

 the wires in the field, so that they may give their aid 

 in estimating the divisions of the scale. The coinci- 

 dence of the disc with one of the wires, or its situation 

 in the middle of one of the intervals between the wires 

 indicates one, two, or three tenths of a second. All 

 the indices move in the same direction as the star, 

 and there is a detent for stopping the wheel work, 

 and a lens near the eye for enabling it to read off 

 the minutes, and the tens of seconds on the dial-plate 

 EF. 



An account 

 of Bre^u- 

 et's eye 

 piece chro- 

 nometer for 

 counting 

 fractional 

 parts of a 

 second. 

 I'LATE 

 CCCCI-XXJJT. 

 Fig. 6. 



