Jan. 3, 1884] 



NA TURE 



219 



the reflectoi- to the heater. Yet we find that an increase 

 of the number of reflecting plates increases proportionably 

 the power of the motor. Considering that the parallelism 

 of the rays absolutely prevents augmentation of tempera- 

 ture during the transmission, it «ill be asked: What 

 causes the observed increase of mechanical power? Ob- 

 viously, the energy produced by the increased density of 

 the rays acting on the heater. The truth of the Newtonian 

 doctrine, that the energy increases as the density of the 

 ra)s, has thus been verified by a practical te;t which 

 cannot be c|uestioned. It is scarcely necessary to observe 

 that our computation of temperature — 1,303,640° Fahr. — 

 does not show maximum sobr intensity, the following 

 points, besides atmospheric absorption, not having been 

 considered : — (i) The diminution of energy attending the 

 passage of the heat rays through the substance of the 

 reflecting plates ; (2) the diminution consequent on the 

 great amount of heat ridiated by the blackened surface 

 of the heater ; (3) the diminution of temperature in the 

 heater caused by convection. J. Ericsson 



A CHRISTMAS VISIT TO BEN NEVIS 

 OBSERVATORY 

 A LTHOUGH I have no tale of perilous adventure or 

 -'*■ hair-breadth escape to tell the readers of Xaiure, 

 yet I think that they will be interested to hear of the pro- 

 gress that is being made in the first British attempt at the 

 cultivation of high-level meteorology. This interest 

 will be all the greater that the hearty encouragement and 

 support that the Ben Nevis experiment has received from 

 all parts of the United Kingdom has given it the character 

 of a national undertaking. 



As most of the readers of N.\ture doubtless know, the 

 observatory is at present in the experimental stage. A 

 good road to the top with bridges and waterways has been 

 made, and a part of the building erected sufficient to 

 shelter the observers. It was judged wise to build as 

 little as possible, until experience should have taught us 

 the peculiar difficulties to be contended with in the some- 

 what novel circumstances presented by the summit of Ben 

 Nevis in winter time. For, although several high level 

 meteorological observatories, and indeed many other 

 human habitations, already exist at much greater heights 

 above the sea, yet there is probably no spot at present 

 inhabited all the year round that presents climatic vicissi- 

 tudes so remarkable. When winter is over, the directors 

 will have a full report, with practical suggestions from the 

 superintendent, Mr, Omond,to guide them in their further 

 operations. Still it was thought well that some of the 

 governing body should see with their own eyes the state of 

 the obser\-atory. and the work of the observers during the 

 cold season. Accordingly two of them (Mr. John Murray 

 and myself) made a visit of inspection on December 26th, 

 of which I propose to give a few particulars. 



•Accompanied by Mr. Maclean, the contractor for the 

 road and observatory buildings, we started from Fort 

 William about 9.30 on Wednesday morning. At first the 

 sky was dark and gloomy, and it was thought that Ben 

 Nevis was to give a specimen of his worst weather. It 

 was not cold howe\'er : in fact it was oppressively warm 

 during the first thousand feet of the ascent from the farm 

 of Achantie where the new road begins. This, coupled 

 with the fact that the pony which one of the party rode 

 up the first 2500 feet of the hill somewhat forced the 

 pace, made it a little uncomfortable for the two pedestrians. 

 The newly made road, loosened by the frost, and sodden 

 by the rain and melting snow, was in places very heavy. 

 Up as far as the little lake (Loch an Meall aut Suidhe), 

 however, the roadway had suffered no substantial damage, 

 except that the fall of a large stone had carried away a 

 small piece of the margin ; and all the bridges and water- 

 ways were found in excellent condition. This is very 

 satisfactory, for the snow has already been down to Fort 



William ; and recently a very rapid thaw has carried it so 

 completely away, that on the 26th very little was met 

 with under 3000 feet. The test has thus been tolerably 

 severe and yet up to 2600 feet or so the road on the, 26th was 

 in far better condition than it was on the day of the opening 

 ceremony. About the altitude just mentioned, a part of 

 the road had been badly ploughed up by a spate of water 

 from the melting snow ; higher up still, the damage seemed 

 to be less, but it was not so easy to judge, as the roadway 

 was there gradually lost in the overlying snow. 



As the party rose in height, the temperature of the air 

 and the ardour of the pony alike fell, and then the walkers 

 were left to the full enjoyment of their climb. During 

 the latter part of the first 3000 feet, the mist had been so 

 thick that the pony and its rider could scarcely be dis- 

 cerned a few yards oft'; but several hundred feet higher, 

 after the road had been finally lost sight of in the snow' 

 and all the p,irty were on foot, we suddenly emerged about 

 noon from the gloom of the mist into the brightest of 

 daylight. Overhead the sky was blue, a fresh light breeze 

 was blowing, and the reflected sunlight was shining in 

 silvery masses on the undulating surface of the frozen 

 snow. We soon reached Buchan's Well, the position of 

 which had been marked by a wooden pole ; but the well 

 itself was completely hidden by a deep snow-drift, which 

 filled the hollow in which it lies. From this spot to the 

 top, the ascent was made almost straight over the snow. 

 At times it was steep and slippery, but the surface was so 

 hard that we rarely sank over the ankles. Two of us 

 were rough shod, one having a few cricketer's spikes 

 screwed to the soles of his boots, the other a pair of 

 steigeisen (climbing irons), the use of which he had learned 

 several years ago during some excursions in the Tyrolese 

 Alps. Mr. Maclean, who had not taken these precautions, 

 fell once or twice, but fortunately without being hurt in 

 any way. When near the last slope we descried 

 Mr. Omond hacking away most assiduously with an ice- 

 axe to prepare a way for us, a needless precaution as far 

 as the rough-shod members of the party were concerned. 

 The view from the plateau on the summit was magnifi- 

 cent. All round there floated a billowy ocean of white 

 mist, from which rose masses of the same, piled up m 

 places like mountain ranges, and through which rose here 

 and there black mountain peaks (prominent among these 

 .Schiehallion). Away towards Fort William was stretched \ 

 black curtain of mist in striking contrast with the snow- 

 whiteness of the upper layer. Down in Glen Nevis a 

 similar mass was seen, rolled and twisted by the air- 

 currents into the most fantastic shapes. So grand was 

 the spectacle that one of our party insisted that we had 

 before us the model from which Dante had drawn his 

 vision of the entrance to hell. 



The summit reached, the directors naturally looked 

 around for the building, whose site they had chosen 

 some five months before, and upon whose construction 

 they had expended so much anxious thought. There was, 

 however, nothing to be seen but two small dark-looking 

 stumps rising a little over the surrounding snow-flat, and 

 alongside of these a little mound of snow. The stum]5s 

 turned out to be the chimney and ventilator on the ro if 

 of the observatory, and the mound was a portico built I y 

 the observers with blocks of frozen snow to protect 1. 

 snow staircase which had been carried down the side ot 

 the house to the doorway. After descending under the 

 translucent canopy and stumbling for a little in the un- 

 familiar darkness of the passage, we entered the main room 

 of the observatory, which for the present serves as sitting- 

 room, kitchen, and office combined. Here we found the 

 table laid for our lunch ; and very soon we were comforting 

 ourselves with hot coffee, cabin biscuits, and excellent 

 Danish butter from the stores of the establishment. The 

 whole ascent had occupied a little over three hours and 

 a half 



The little room in which we sat contained the American 



