November 3, 1892] 



NATURE 



'9 



dust-cloud. The spots observed on Jupiter's surface are next 

 dealt with, a table of their rotatioa periods and latitudes 

 being included. From the latter he deduces that the mean 

 periods of rotation of matter in the following latitudes are : — 

 Lat. h. m. s. 



12° N. from 17 N. Temp, spots 9 55 36*49 

 4° N. ,, 5 N. Equat. ,, 9 50 40-06 

 8° S, ,, 21 S. Equat. ,, 9 50 22*4 



30" S. „ 3 spots 9 55 17-1 



In treating of the spots themselves, he suggests that those which 

 are of a white appearance are gyrating uprushes of warm air 

 from the lower regions, while the dark ones are simply descend- 

 ing columns of cool air, " the two forming parts of the system of 

 vertical circulation." The red spot, he suggests, is caused by a 

 local escape of internal heat, the repellent force it appears to 

 possessbeingdue to the "spreading of the heated currents as they 

 rise." He explains the retardation and accelerati )n of its period 

 of revolution by the increasing force of the west winds, brought 

 about by the exposure of the southern hemisphere during Jupiter's 

 half-year (5 '93 of our years) ; in this way the spot is sometimes 

 situated over and sometimes to one side of the source of heat 

 underneath. The author also deals with other spots in a similar 

 manner. 



GEOGRAPHICAL NOTES. 



Mr. Sven Hedin's account of his ascent of Mount Demavend 

 is published in the last number of the Verhatiilun^en of the 

 Berlin Geographical Society. Demavend is a volcanic peak 

 rising abruptly from the s'idimentary rocks of the parallel Elburz 

 chains. Starting from the village of Ranah on the south- 

 eastern slope with two guides on July 10, 1890, Hedin reached 

 the summit on the afternoon of the next day. On the summit a 

 large elliptical crater was found ; the edges of which were strewn 

 with blocks of porphyritic lava and sulphur. After discussing 

 the aneroid and boiling point observations, Mr. Hedin arrived 

 at 5465 metres (17,930 feet) as the height of the summit. This 

 is lower than any of twelve earlier estimates which are cited, the 

 highest of them being 6559 metres. 



The Italian possession of Eritrea on the coast of the R^d Sea 

 gives some promise of becoming useful agriculturally. Several 

 small settlements of Italians on the plateau have succeeded in 

 growing large crops of wheat and barley, and only the unsettled 

 state of the surrounding natives threatens the prosperity of the 

 farmers. The districts of Ocule-Cusai and Guro are already 

 fully cultivated, and Sarae, as yet almost unoccupied, has fertile 

 land and plenty of room for colonists. The Italians are able to 

 work in climatic conditions which would rapidly exhaust the 

 natives of northern Europe. 



The general summary of Mr. Conway's expedition in the 

 Karakoram range telegraphed from India (p. 525) has now been 

 supplemented by a full narrative, written to the secretaries of 

 the Royal Geographical Society from a camp on the Baltoro 

 Glaciv-r on August 29, with a postscript added at Skardo, on the 

 way to Leh, on September 12. The difficulties of the pre- 

 liminary journey were very great, not the least being the fording 

 of several swollen glacier streams by a party numbering four 

 Europeans, four sepoys, seventy coolies, an indefinite number of 

 followers, and flocks of goats and sheep. The moraines on the 

 Baltoro glacier were of almost incredible extent ; for two-thirds of 

 its entire length the ice is entirely concealed by stones, except where 

 crevasses or lakes occur, and the irregularity of the surface made 

 travelling extremely slow. Mr. Conway limits the name 

 of Godwin-Austen to the highest peak of " K-," giving 

 to the whole mountain the somewhat cumbrous* title 

 of the Watch Tower of India. One branch of the 

 Baltoro Glacier results from the union of seven glaciers 

 from this mass ; the larger branch descends from the 

 snow-swathed, throne-shaped mountain, hitherto unmapped, 

 for which the auriferous quartz found in its rocks suggested 

 the name of The Golden Throne. This was fixed upon as the 

 goal to be attained. The first attempt landed the Europeans 

 and Ghoorkas, who made excellent climbers, on Crystal Peak, 

 20,000 feet in elevation, a peak as hard to climb as the Matter- 

 horn, and isolated from the surrounding higher summits. No 

 inconvenience was felt from the rarity of the air, and the party 

 remained on the summit for an hour and a quarter. In the 

 grand attempt on the Golden Throne serious difficulty was en- 



NO. 1 201, VOL. 47] 



countered from the terrible extremes of heat and cold. The 

 last few thousand feet proved very exhausting ; one of the 

 Ghoorkas had to be left behind, suffering from mountain-sick- 

 ness. Every step had to be cut in hard ice. Finally the summit 

 was reached at an elevation of 23,000 feet ; but the Golden 

 Throne stood revealed much higher, and separated by a deei> 

 depression. From the summit of Pioneer Peak, probably the 

 highest yet reached by man, a series of photographic views was 

 obtained and prismatic compass bearings taken to the surround- 

 ing features. As long as the party were at rest they felt no 

 discomfort, but the sphygm(>graph showed that the heart's 

 action was very laboured. A stay of an hour and a quarter 

 was made on the summit, the view from which baffled descrip- 

 tion. The descent was safely made, but fatigue and bad weather 

 stopped farther exploration. 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS. 



C\^ the evenings of Wednesday and Thursday of last week, the 

 ^-^ 26ih and 27lh ult., an ordinary general meeting of the Insti- 

 tution of .Mechanical Engineers was held in the theatre of the In- 

 stitution of Civil Engineers, by permission of the council of the 

 latter Society. The President, Dr. William Anderson, occu- 

 pied the chair during the proceedings. 



There were two papers on the agenda. The first was the 

 report of the Institution's committee appointed to enquire into 

 the value of the steam jacket. Mr. Henry Davey is the chair- 

 man of this committee, and he had prepared the report ; 

 which is a bare record of facts without comment, and in this 

 respect is, we think, defective. Numberless experiments have 

 been made in time past as to the value of the steam jacket, and 

 those now added by the labours of the committee do not largely 

 difTer from many that have gone before. We take it that the 

 general opinion of competent engineers is that an advantage in 

 efficiency is to be obtained by jacketing engine cylinders in an 

 efficient manner, and cases in which the jacket has not been 

 proved efficient are those in which it has not been properly ap- 

 plied. What was wanted, therefore, was guidance as to the 

 proper method of application, and it is significant that the 

 most help in this direction came, during the discussion, from 

 those who were not members of the committee. Timidity in ex- 

 pressing opinion will be excusably construed as indicating some- 

 thing of incompetence, and if the members are not capable of 

 expressing opinion they are not suitable persons to form a research 

 committee of an important institution. We frame our remarks 

 hypotbeticaljy, because, with such names as Unwin, Bryan Don- 

 kin, and Mair-Rumley on the title-page, there can be no doubt 

 that the power to aflbrd guidance was present, and for this 

 reason the decision to give only bare fact is the more to be re- 

 gretted. The general conclusion to be drawn from the 

 experiments, as quoted, is that "the expenditure of a quantity 

 of steam in an efficient jacket produces a saving of a 

 greater quantity in the cylinder." It does not follow 

 from this that the jacket is always desirable, as the saving may 

 be so small as not to justify the additional complication and 

 increased outlay at first cost. That, however, is a matter 

 upon which steam users must themselves decide upon a com- 

 mercial ba>is ; and is, of course, outside the province of the 

 committee, but what would have been valued would have been 

 some critical remarks giving guidance as to what goes to con- 

 stitute the " efficient jacket," what fresh engineering practice is 

 opened up by the use of the efficient-jacket, and under what con- 

 ditions it may be most effectually applied. 



The first series of experiments quoted were carried out by 

 Mr. J. G. Mair-Rumley, of the firm of James Simpson and Co., 

 of Pimlico, upon a compound jet-condensing beam pumping- 

 engine. The diameters of the cylinders are 29 inches and 

 475 inches, with strokes of 651 nnd 96 inches respectively. 

 Only the body of each cylinder is jacketed, the steaiii being 

 supplied direct from the boiler at a pressure of 49lbs. per square 

 inch above atmosphere. Experiments were made both with 

 and without steam in the jackets. The total feed water per 

 indicated horse power per hour when the jackets were not in 

 use was i8"2olbs., with the jackets in use the corresponding 

 figures were 1664 Ihs., thus showing a percentage of less steam 

 u>ed due to the jackets of 8-6. 'Ihe quantity of jacket water 

 condensed was I -20 lbs. per I. H. P. per hour. The boiler pressure 

 here was not high, 497 lbs. without and 49 lbs. with jackets. 



