492 



NATURE 



{March 25, 1880 



bination in which they cannot be recognised by the spectroscope 

 (which is also hardly admissible at that elevated temperature"), or 

 that they have been decomposed." 



The important work of Victor Meyer on the behaviour of 

 chlorine and iodine at elevated temperatures which must now be 

 regarded as finally established by the experiments of which an 

 account is given in the recent number of the Berichteder deals. '.::: 

 chemischen Gcsdlschajl (March, 1S80), and on which 1 ventured 

 to offer some theoretical considerations ina paper which appeared 

 in the J. Chan. Soe. last autumn, point in the same direction. 

 It is difficult not to admit the force of such a body of coincident 

 evidence as that of which I have here given a brief outline. 



March 14 B. C. Brodie 



The Aurora at Last 



YESTERDAY, Wednesday, March 17, was a magnificently 

 bright sunshiny day from early morning to latest evening ; and 

 at 9 p.m. the aurora appeared, just as it used to do years ago in 

 the last sun-spot cycle, and when that strange influence was in its 

 in as existence, V ur readers were warned last October 

 that the sun-spots of the new cycle had then begun "in earnest," 

 and now we have to chronicle the first of their auroral fruits. 



It was a long low arc of mild quiescent light, about 2" in 

 transverse breadth, 20° long, rising about 7° high in the middle, 

 and sensibly dark between its lower edge and the horizon; the 

 centre was over the north-northwest point of the horizon, but 

 swayed slowly several degrees of azimuth on either side. To- 

 wards 11 p.m. the arc began to break up into brighter pellets of 

 light, and these shot fainter rays upwards, making a brilliant 

 and variegated appearance for a few minute-, but apparently 

 soon exhausting itself, for after that there remained only a faint 

 image of the arc up to 1 a.m. ; all this being clearly 

 visible; to the naked eye, although a moon seven days old an-1 in 

 24" N. Deck was shining brightly in the west. 



In the spectroscope, with a narrow slit, nothing but the one 

 inscrutable citron-coloured line appeared, its place in wave- 

 numbers, per British inch, and as ascertained in both hydrogen 

 and carbonic oxide vacuum tu_es, being between 45592 and 

 45 6 9°- Fiazzi Smyth 



15, Royal Terrace, Edinburgh, March iS 



A Museum Conference 



Allow me to deprecate most strongly any attempt to form an 

 association having for its object to talk about museums. Museum 

 officials either know their business or they do not. In the former 

 case they have 5 jmething better to do than to talk ; in the second 

 case the less they say the better. '1'he multiplication of con- 

 threatens to become a nuisance, aud special conferences 

 for even- grade, class, and description of humanity will soon be 

 proposed by fussy idlers. We shall be told that it is time to 

 have a conference of housekeepers, of lamplighters, of railway 

 guards, boot-makers, beadles, perhaps ballet-girls. 



The fact is that endless time and trouble and money are wasted 

 in England in maintaining rubbishing local museums in the care 

 of ignorant aud pretentious curators. Conferences are not 

 required, but proper salaries for the curators, who should be 

 educated and capable meu ; were such men secured by adequate 

 salaries they would soon make the museums in their charge very 

 different from what they now are. 



A curator with proper salary ought to be made to attend daily 

 at his museum dining office hours, aud not allowed to leave it to 

 take care of itself whilst he is lecturing here or there, or eking 

 out his pay by literature. ACADEMICUS 



I am glad to see that Mr. Paton has, in Nature, vol. xxi. 

 p. 442, again revived the subject of a museum conference, and 

 offers to give his aid towards such attaining a practical form. 

 The desirability of a Museum Association was first suggested in 

 an article in Nature, vol. xv. p. 276, and this was followed 

 by a more definite proposal for a conference by "J. P.," and 

 with the addition of a letter in favour of the same object by Dr. 

 Meyer nothing further was published about it. This looked as 

 if the subject was not considered of any great importance, but I 

 believe many curators were decidedly in favour of it, and only 

 i assuming a practical form to give it their hearty sup- 

 port. The success which has attended the Library Association 

 give- every reason to believe that the formation of a similar 



association of museum officials would lead to equally good 

 results. Apart from the benefits to be derived from an inter- 

 change of ideas and results of experience, which, considering the 

 varied nature of museums and the many practical questions 

 involved in their succe-sful management, could not fail to be 

 considerable, there are many things affecting provincial museums 

 generally that would be greatly advanced by united action. One 

 of these, the distribution of the British Museuin duplicates, I 

 should like to refer to. In the British Museum Removals Bill a 

 clause was inserted at the instigation of Mr. Mundella, M.P., 

 and Mr. Chamberlain, M.P., which states that "the Trustees of 

 the British Museum may also give away any duplicate works, 

 objects, or specimens not required for the purposes of the 

 Museum." Instead of giving away, however, I learn that the 

 Trustees are about to sell by auction some of the duplicate prints, 

 drawings, &c, in the Museum ; aud fearing that other dupli- 

 cate, might be disposed of in a similar manner I had the matter 

 brought before Mr. Mundella, who obtained an interview with 

 the Right Hon. Spencer Walpole, Chairman of the Trustees, 

 and wa; informed that instructions had been given for duplicates 

 in the Natural Hi-tory Departments to be laid aside and cata- 

 logued for distribution among the principal museums. This is 

 reassuring, but why not treat all their duplicates in 

 this way? — for it should be remembered that provincial towns 

 contribute their share of imperial taxes. 



I must not, however, occupy your valuable space with matters 

 that ought properly to be discussed by such a conference as Mr. 

 Paton suggests; and I hope that all who are interested in 

 museums will heartily co-operate with Mr. Paton, whose great 

 success ia developing the museum at Glasgow and his extensive 

 acquaintance with museums both in Britain and on the Continent, 

 eminently qualify him to speak with authority on the subject. 



Sheffield Public Museum, March 23 E. HOWARTH 



A Method of Calculating the Expansion of a Substance 

 on Vaporisation 



Having occasion last summer to determine thei-volume of gas 

 which would result from the vaporisation of a given quantity 

 of a certain solid, I made use of a simple way of obtaining 

 approximate results which may not prove uninteresting to some 

 of your readers, unless, as is very likely, they have already made 

 u-e of it or a better way themselves. For purposes of illustra- 

 tion we may take it that I gram of hydrogen gas^ occupies a 

 volume of 11,200 c.c. at normal pressure and temperature; 

 moreover, the weight of I c.c. of water is I gm. at o" C. 



Knowing the atomic weight and specific gravity of any liquid 

 or solid, we can now find the volume which 1 c.c. of it will 

 assume on passing into the gaseous state by a simple "rule ol 

 three" sum. 



For the weight of I c.c. of the substance is given by the 

 number which indicates its specific gravity ; and the weight of 

 1 1,200 c.c. of its gas is given by its atomic weight. 



Hence 



sp. gr. 

 at. v. t. 

 to which I c.c. of the substance expands on becoming gaseous. 



It is interesting 



11,200 = vol., 



cal of — ' ', which is the expression for the so-called atomic 



sp. gr. 

 volume (v) of a substance, and thus the expansion of I c.c. of a 

 solid or liquid as it becomes gaseous may also be determined 

 by dividing the number 11,200 by the atomic volume of the 

 substance. 



In this way we find that I c.c. of sodium will occupy 474 c.c. in 

 the state of gas, and I c.c. of potassium 249 c.c, or, what is 

 the same thing, I c.c. of each of these substances in the gaseous 

 state will occupy -ji T c.c. and ,\ v c.c. in the solid state respec- 

 tively. But equal volumes of gas under the same conditions ot 

 temperature and pressure contain an equal number of molecules, 

 and hence ^fi c.c. and ^cc, the products of the condensa- 

 tion of equal volumes of" potassium and sodium gas must contain 

 an equal number of molecules. From this we readily deduce 



a real physical meaning for the fraction — : — ', or, in other 



words, for the expression "atomic volume," the significance of 

 which, at first, was merely conjectured. 



Lists of homologous series of elements and compounds, with 

 their "condensation numbers" attached, give very interesting 

 results ; I have only one such at hand, which I here give : — 



