February 14, 1895] 



NA TURE 



377 



and iron hail and iron rain, and so on, falling upon the photo- 

 sphere as the rain falls on the earth. There is thus a possi- 

 bility in the sun of home made meteoritic action. 



So far as my last course of lectures was concerned, I there 

 ended that part of the subject. IJut so many points bad been 

 raised in trying to give a connected view of these two very 

 slowly converging lines of research to which I referred, that, after 

 the lectures were over, I determined to discuss the various 

 points which had been raised. I determined to take up 

 Prof. Tait's suggestion, and see how all the spectrosc 'pic obser- 

 vations which had been made up to the time of my lectures in 

 1886, bore out that suggestion which had been made in 1S71, 

 before there was very much spectroscopic evidence to go upon. 

 The result was that my assistants and myself spent something 

 like three years in gathering together, we believe, every avail- 

 able observation ; at all evenis, if not every available observa- 

 tion, there were between thirty and forty thousand of them, and 

 we found that a very considerable number. I not only deter- 

 mined to collect them, but also to discuss them, and make any 

 experiments or observations which might be suggested by the 

 discussion. The result of this was that, as a fruit of that course 

 of lectures, several papers, some of them very long — it is not 

 for me to say anything as to their value — were sent in to the 

 Royal Society, and eventually brought together in a book. 



Now, what I found was that when we discussed the 

 meteoritic view in the light of all the ol)servations we could get 

 together, and in relation to stars as well as nebula: and comets, 

 it seemed to explain many things, and threw a perfectly new 

 light upon the visible universe ; there were, moreover, several 

 points raised of intense novelty and freshness, each of which 

 could be discussed separately, cast aside if it were false, and 

 held on to if it were true. I give a table of some of these new 

 points of view. 



New points of view in the Meteoritic Hypotiiesii. 



(1) There is the closest possible connection between nebuhe 

 and stars. 



(2) The first sta'Te in the development of cosmical bodies is 

 not a mass of hot gas, but a swarm of cold meteorites. 



(3) Many bodies in space which look like stars are really 

 centres of nebulae ; that is, of meteoritic swarms. 



(4) Siars with bright-line spectra must be associated with 

 nebula;. 



(5) Some of the heavenly bodies are increasing their tem- 

 peratures ; others are decreasing their temperatures. 



6) Double swarms, in any stages of condensation, may give 

 rise to the phenomena of variability. 



(7) New stars are produced by the clash of meteor swarms. 

 They are closely related to nebul.L and bright-line stars. 



(8) Cosmical space is a meteoritic plenum. 



(9) A new classiiication of the heavenly bodies, based on the 

 varying states of condensation of the meteoritic swarms. 



(10) The sun is one of those stars the temperature of which 

 is rapidly decreasing. 



(11) Many of the changing phenomena of the sun are due to 

 the fall of meteoritic matter upon the photosphere. 



We ultimately arrived at the conclusion that the .sun is one of 

 the stars, the temperature of which is gradually decreasing, 

 and that many of the phenomena of the sun are due to the fall 

 of meteoritic matter on the photosphere. 



The doing of a large piece of work like that — and I .say it is 

 large because I am glad to have the opportunity here of ex- 

 pressing my gratitude to my asistants, who stood by me for 

 three years — brings one out pretty well into the open, and 

 renders one liable to a brisk fire of criticisms, some very valuable, 

 some quite unworthy of the critics. 



You will see that the work was undertaken with a view of 

 determining the sun's place among the stars. 



J. Noi;man Lock\ liK. 

 (To be continued.) 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS. 

 'T'HF. annual general meeting of the Institution of Mechanical 

 •*■ Engineers was held on Thursday and Friday evenings, 

 the 31st ult. and the 1st inst. Prof. A. B. W. Kennedy, !•". R. S., 

 occupied the chair. There were two papers set down forreading 

 and discussion : 



*• The Determination of the Dryness of Steam." I'.y Prof. 

 W. Cawthorne Unwin, I'. U.S. 



I 



"Comp.irison between Governing by Throttling and by 

 Variable Expansion." By Captain H. Kiall Sankey. 



Prof. Unwin, in his interesting paper, gave descriptions of the 

 best known methods oldetermining the mean of moisture in steam 

 up to now introduced. Most of the apparatus described was 

 exhibited on the talile of the theatre, whilst diagrams illustra- 

 tive of them were hung on the wall. The author pointed out 

 that the earliest attempts to determine the amount of moisture 

 in steam, of which records have been found, were made during 

 some boiler trials carried out by a committee of the Societe 

 Industiielle of Mulhouse in 1859. This committee tried three 

 difierent methods — a method of separation, a condensing 

 method suggested by Hirn, and a chemical method. In these 

 early trials the condensing method only, in which the total 

 heat of a sample of the steam was measured, appeared to give 

 saii-facloiy result ~. But although the committee did not place 

 full reliance on any of their methods, these have all been used 

 by various experimenters down to the present time. 



The origin of water entiained in steam. Prof. Unwin said, 

 was to be attributed to three causes : 



(i) Water projected into the boiler's steam space during ebul- 

 lition. The extent to which wetness occurs depends on the 

 activity of the ebullition, the area of the water surface, the 

 volume of the steam space, the position of the steam valve, the 

 density of the steam, and. probably more than anything else, 

 on the quality of the water and its liability to produce foam. 

 The author referred to the experiments of Mr. Thorny- 

 croft, who constructed a boiler with glass ends, through 

 which the process of boiling could be sten. The result of 

 oljservations on this boiler showed ' that waters which cause 

 primmt; produce foam on boiling. Water which is very bad 

 produces bubbles so durable as to remain a considerable time 

 without breaking ; and by them the steam space of a boiler may 

 be entirely filled. So soon as this takes place, instead of simply 

 .steam leaving the boiler, the ilischarge consists of foam, which 

 becomes broken up in its rapid passage through the steam-pipe. 

 With pure water, steam retains no film of liquid long enough to 

 be seen. 



(2) Water may be produced in steam from the expansions to 

 which it is subjected. Fluctuations of pressure arise from the 

 intermittent demand for steam, and from the steam passing from 

 places of higher to places of lower pressure. Prof. Unwin con- 

 sidered it difficult to believe that any great amount of wetness 

 arises in this way in ordinary cases. 



(3) The steam in the boiler, and the steam-pipes, loses heat 

 by radiation. Probably in some cases considerable wetness is 

 produced in this way. The wetness of the steam, so far as it is 

 due to this cause, will increase a; the demand for steam 

 diminishes. 



The author next went on to deal with the various methods of 

 determining the wetness of steam, referring first to the weighing 

 method, by which a known volume is weighed, when any excess 

 of weight above that of a corresponding volume of dry saturated 

 steam must be due to the water present. This method is 

 obviously one of excessive difficulty. 



The sujierheating method was next referred to in the paper, 

 the experiments of Barrus and Carpenter being quoted. The 

 Carpenter calorimeter consists of a vessel about 12 inches 

 high by 5 inches diameter, consisting of an inner chamber and 

 a jacket. The steam from the steam-pipe passes first to the 

 inner chamber, where the moisture is separated, .and then into 

 the outer chamber. The separating chamber is therefore per- 

 fectly protected from radiation. .Vs the water accumulates in 

 the inner chamber, its level is shown by a gauge glass, .and the 

 amount in hundredths of a pound can be read otT on a scale. 

 A very small orifice at the bottom of the outer chamber regulates 

 the amount of sleam discharged. The escaping steam passes 

 through a llexihle tube to a simple form o( condenser. The 

 increase of weight in any given time in the condenser is noted, 

 and the amount accumulated in the same time in the separator. 



The condensing method was next described. This is founded 

 on the condensation of a known weight of steam and the deter- 

 mination of its total heat by the rise of temperature in the 

 condensing water. By comparing the total heat per pound of 

 a sample of sttam with that of a pound of dry saturated steam 

 according to Regnault's tables, the amount of moisture in the 

 steam can be determined. This method was first suggested by 

 Hirn, and the apparatus which he designed is perhaps the most 



> " Circulation in the Thornycroft Water-Tule Boiler." Tianmiihtis of 

 the Inslitulton of Nav.-il Archirects, :S94. 



NO. «.320, VOE 



51] 



