58 



NATURE 



[November 12, 1908 



The structures observed in lead-tin eutectic alloys are 

 describSed in detail, and evidence is given for the view 

 that this alloy consists of an aggregate of spherulitic 

 crystals. The authors have also examined the structure 

 of " alloys " prepared by the compression of powders 

 (Spring's method), and have found them to consist of 

 aggregates of the original particles in an unchanged con- 

 dition. 



" The Boiling Point of Sulphur on the Constant 

 Pressure Air Thermometer." By N. Eumorfopoulos. 

 Communicated by Prof. H. L. Callendar, F.R.S. 



The experiments described in this paper were carried out 

 with a view to the re-determination of the boiling point 

 of sulphur, the value (444°-53) previously obtained by 

 Callendar and Griffiths being open to some doubt. 



The air thermometer, made of Jena glass i6in., is 

 substantially that described by Callendar (Roy. Soc. Proc, 

 vol. 1., p. 247), except that the final adjustment of pressure 

 is made with the help of an oil gauge. 



The formula to be used with this thermometer is shown 

 to take a simple form, the necessary corrections being 

 small. In particular, the uncertainty of the temperature 

 of the " dead space " is eliminated by means of com- 

 pensated tubes. The sensitiveness of the oil gauge is given 

 for different temperatures, and its diminution with rise of 

 temperature shown to have little practical importance. 



-■Ml the volume determinations are made with mercurv. 

 The expansion of the bulb was obtained by treating it as 

 a weight thermometer, observations being made at o°, 

 100°, and 184°. If the Regnault-Broch formula for the 

 expansion of mercury is taken, the experiments lead to 

 the following expression for the coefficient of expansion 

 of the glass, 



;2!86S + 4-20(/- 100); 10-", 

 but with Chappuis's value to 



{24254 + 23 •47(/- ioo)|io"^ 



Reasons are given for preferring the former value, thus 

 suggesting that the true value for the coefficient of 

 expansion of mercury is still unknown. 



The boiling point of .sulphur was determined directly on 

 the air thermometer ; the mean of the eleven values 

 obtained is, at normal pressure, 443°.62. 



The changes of volume of the bulb when heated in 

 sulphur vapour were a source of trouble and some un- 

 certainty, although the bulb had been previouslv annealed 

 for many hours. 



"Note on the Boiling Point of Sulphur." By Prof. 

 H. L. Callendar, F.R.S. 



_ One of the chief difficulties in the accurate determina- 

 tion of high temperatures by means of the gas thermo- 

 meter is the uncertainty of the correction for the expansion 

 of the bulb. The whole correction may amount to as 

 much as 5° C. at 445° C. (the boiling point of sulphur) 

 or 30° C. at 1000° C. The uncertainty of the correction 

 is due to the fact that it cannot be directly determined, but 

 must be inferred from observations of the linear expansion 

 of the material of the bulb, or from observations with a mer- 

 cury weight thermometer, in which the expansion of mercurv 

 is assumed. There are obvious objections to assuming 

 that the cubical coefficient of expansion of an asvmmetrical 

 bulb is three times the linear. The method of the mercury 

 weight thermometer would be theoretically perfect but for 

 the fact that the temperature range available is somewhat 

 restricted, and that the absolute expansion of mercury is 

 more or less uncertain. The extrapolation of the observa- 

 tions beyond 300° C. is attended with some uncertainty, 

 and the differences of the formulas proposed to represent 

 the expansion of mercury, though inconsiderable at low 

 temperatures, become important when extrapolated. The 

 value of the boiling point of sulphur hitherto assumed as 

 the basis of the platinum scale of temperature, namely, 

 '*44 '.^j C., depends on the determination of the correction 

 by _ the linear expansion method alone. It appeared 

 desirable to corroborate this result bv the weight thermo- 

 meter method. 



With this object, Mr. Eumorfopoulos undertook a series 

 of observations with a very delicate gas thermometer of 

 NO. 2037, VOL. 79] 



Jena glass, the bulb of which was fitted to serve also as 

 a mercury weight thermometer. The results of the several 

 independent series of observations agreed among them- 

 selves to less than a tenth of a degree at the boiling point 

 of sulphur, but differed by about 2° C. in the absolute 

 value of the boiling point according as the formula of 

 Regnault or that of Chappuis was adopted for the ex- 

 pansion of mercury. The value, according to Regnault's 

 formula, was 443°-6 C, but it was 445°-8 C. according 

 to the formula of Chappuis. Arrangements have in the 

 meantime been made for the re-determination of the 

 absolute expansion of mercury at the Royal College of 

 Science, and it is hoped that the results of this work, 

 which will be applicable to the reduction of previous 

 observations, such as those of Mr. Eumorfopoulos, will 

 reduce materially the present uncertainty. 



" The Spectrum of Scandium and its Relation to Solar 

 Spectra." By Prof. A. Fowler. Communicated by Sir 

 William Crookes, F.R.S. 



The greater part of this investigation of the spectrum 

 of scandium under different experimental conditions has 

 been based on purified scandia, generously placed at the 

 author's disposal by Sir William Crookes. The principal 

 results are as follows :- — 



(i) The arc spectrum of scandium consists of two dis- 

 tinct sets of lines, which behave very differently in solar 

 spectra. Each set includes both strong and faint lines. 



(2) Lines belonging to one set correspond with the 

 enhanced lines of other elements, notwithstanding that 

 they appear strongly in the ordinary arc spectrum : — (a} 

 these lines are very feeble or missing from the arc-flame 

 spectrum, and are strengthened in passing to the arc, the 

 arc in hydrogen, or the spark ; (6) they occur as relatively 

 strong lines in the Fraunhofer spectrum ; (c) they are 

 weakened in the sun-spot spectrum ; (rf) they occur as 

 high-level lines in the chromosphere. 



(3) The remaining lines show a great contrast when 

 compared with the first group : — (a) they are relatively 

 strong lines in the arc flame ; (b) they f e very feebly re- 

 presented in the Fraunhofer spectrum ; (r) the stronger 

 lines are prominent in the sun-spot spectrum ; (d) they have 

 not been recorded in the spectrum of the raromosphere. 



(4) The special development of the enh.' need lines in the 

 Fraunhofer spectrum, together with their presence in the 

 upper chromosphere, indicates that the greater part of the 

 scandium absorption in the solar spectrum originates at a 

 higher level than that at which the greater part of the 

 iron absorption is produced. 



(5) The discussion of scandium lines indicates that while 

 In the case of some elements solar identifications are to be 

 based chiefly on arc lines, in others it is the enhanced lines 

 which may be expected to show the most important 

 coincidences. 



(6) The flutings which occur in the arc and arc flame 

 do not appear when the arc is passed in an atmosphere 

 of hydrogen. k% suggested by Thal^n, they are probably 

 due to oxide of scandium. 



Tables are given which show the lines of the arc spec- 

 trum from 3030 to 63S0, the positions of the oxide flutings, 

 and comparisons of the principal lines of the two classes 

 with the sun, sun-spots, and chromosphere. 



Edinburgh. 

 Royal Society, November 2. — Prof. A. rjray, vice-presi- 

 dent, in the chair. — Temperature observations on Loch 

 Garry ; E. M. Wedderburn. The observations were made 

 during the first seven months of 190S by means of reversing 

 mercury thermometers, and led to the following general 

 results : — (i) the observations give a complete series for the 

 time of year during which the lake is gaining heat, so th.nt 

 comparisons may be made between Loch Garry, of com- 

 paratively small size, and Loch Ness, of much larger size ; 

 (2) they show the apparently fortuitous manner in which 

 freezing may take place in the larger temperate lakes ; 

 (■?) they show how strong winds have the effect of pro- 

 ducing currents at considerable depths ; (4) they prove that 

 the formation of the discontinuity temperature layer in a 

 lake occurs whenever the surface layer begins to cool ; 

 (5) they establish the existence of a temperature seiche In 

 small temperate lakes like Loch Garry, and show ihat 



