676 



NATURE 



[February ig, 1920 



for power alone, and a sugar factory an equal 

 quantity of coal for boiling purposes, some means 

 ought surely to be found to bring them together, and 

 thus satisfy both demands with a consumption of 

 23 tons instead of 40 tons. 



In discussing the question of the safety of cast-iron 

 economisers, Mr. Stromeyer gives a summary of all 

 the economiser explosions — seventeen in number — 

 reported upon by the Board of Trade since 1882. Only 

 nine of these explosions were destructive, but, unfor- 

 tunately, none of the inquiries into these mishaps 

 have revealed their true causes. If the Board of 

 Trade inquiries into boiler explosions are to be of 

 value, they ought to be conducted in such a manner 

 that the study of the reports may be of service to 

 engineers who have to design and use the appliances. 

 It would appear, however, that the object which Mr. 

 Stromeyer's association had in view in drawing up 

 the Boiler Explosions Act, 1882, has been entirely 

 lost sight of. It was intended that. every explosion 

 should be investigated by an expert, but it was found 

 necessary, in order to get the Bill through Parlia- 

 ment, to add one competent lawyer to the engineering 

 experts. The lawyer has always been made president 

 of the commission, with results which may be 

 imagined. Further, there are probably very few 

 "competent and independent engineers " who are, as 

 required by the Act, "practically conversant with the 

 manufacture and working of boilers," since few 

 engineers pass through the boiler-shop, and fewer still 

 have had to work them. But the Board of Trade has 

 no hesitation in appointing men to make these 

 inquiries who have never even seen the objects which 

 they have to investigate. At a recent inquiry two 

 investigators, both marine engineers, confessed that 

 they knew nothing about land economisers, neither 

 their design, material, manufacture, nor mode of 

 working. .As the Board uses a rota, the chances 

 are that these engineers will never again be 

 called upon to inquire into an economiser explosion, 

 despite the knowledge they doubtless gained in the 

 course of the inquiry. In these circumstances it is 

 but natural that many preliminary reports, and nearly 

 all Commissioners' reports, dismiss the cause of ex- 

 plosions with a non-committal remark to the effect 

 that " the boiler burst because it could not withstand 

 the steam pressure." 



Mr. Stromeyer suggests, and we strongly support 

 the suggestion, that the duty of investigating boiler 

 explosions should be entrusted to an enthusiastic 

 engineer, who would certainly go into details, and 

 make experiments on the strengths of materials, 

 especially upon the parts of burst boilers, which is 

 scarcely ever done at present ; he would also take 

 steps to become acquainted with the influences of 

 working conditions. 



The memorandum contains ample evidence, extracted 

 from Board of Trade reports, to justifv Mr. Stromeyer's 

 remarks. For example, Report No. 2470, on an 

 economiser explosion, omits to mention certain old 

 fractures. The two " competent and independent 

 engineers" (selected bv the Board from among its 

 own staff), together with other engineers, refused in 

 their evidence to admit that an open damoer could 

 have caused the failure of any of the pipes, and 

 attributed the explosion to the old fractures. Bv 

 withholding this information the report deprives the 

 engineering profession of the means of studviiig the 

 problem of economiser safety. 



The fact appears to be that the investigations are 

 carried out by the solicitor of the Board of Trade, 

 who brings forward sworn evidence, though the swear- 

 ing is not required bv the Act, and without anv 

 warning to the witnesses, these may now be cross- 



NO. 2625, VOL. 104] 



examined both by their own side and by the Com- 

 missioner, and then very often their own sworn 

 evidence is used against them. It is unfair to wit- 

 nesses who wish to give the Commissioners every 

 assistance, and as the whole atmosphere is now a 

 legal one (even a Lord Advocate once appeared for 

 an insurance company) the technical causes of ex* 

 plosions are scarcely inquired into. 



THE BELGIAN ROYAL OBSERVATORY. 

 I T is pleasant to see that the Brussels Observatory 

 ■'■ is in a position to resume the publication of its 

 memoirs (Annals of the Belgian Royal Observatory, 

 vol. xiv., part 2). After a discussion of the division 

 errors of the Repsold meridian circle. Prof. Stroobant 

 contributes an interesting essay on the constitution of 

 the ring of minor planets. Tables and diagrams are 

 given of the distribution of the various elements ; the 

 striking grouping of the perihelia towards Jupiter's 

 perihelion is already well known, and Newcomb gave 

 an explanation of it from theory. The eccentricities 

 show a similar grouping, high eccentricities being 

 most frequent in the quadrants where the perihelia 

 congregate ; this can also be explained by the action 

 of Jupiter. The formulae expressing the perihelion 

 density (N is the number of perihelia in an arc of 

 30°) and the eccentricity are : 



N = 6675 -317 sin (ra-1067') 

 e= 0141- 0'028sin(ra- 86'5'"). 



The ascending nodes show a slight tendency to group 

 towards Jupiter's ascending node ; it would probably 

 be easier to study the relations of nodes and inclina- 

 tions if the elements were referred to the plane of 

 Jupiter's orbit rather than to the ecliptic. 



There is an interesting study of the probable total 

 number of asteroids brighter than niagnitude 20. From 

 some very faint asteroids discovered by photography at 

 the Lick Observatory, combined with the area of sky 

 covered by the plates, the total 57,000 is obtained. 

 From a study of the number of known planets of 

 different magnitudes the empirical law is deduced that 

 the number per magnitude doubles for a fall of one 

 magnitude. On this basis the total number brighter 

 than magnitude 20 is 100,000. The two estimates are 

 in satisfactory accordance, bearing in mind the large 

 measure of extrapolation employed in each method. 



It is estimated that very few asteroids (say twenty) 

 brighter than the 12th mag. at opposition remain to 

 be discovered. 



Taking the mean albedo as 0108 (midway between 

 those of Mercury and Mars) and the density the same 

 as the moon's, the total mass is 1/22 of that of the 

 moon, the planets brighter than magnitude 10 con- 

 tributing one-third of this total, and those between 

 magnitudes 10 and 11 another one-third. 



The third memoir in the volume is on the bright- 

 ness, colour, position, and parallax of Nova .Aquike; 

 a large-scale light curve is given extending from 

 iqi8 June 10 to November 23. From the end of June 

 until the middle of August there were fairly regular 

 oscillations in the curve, the period being thirteen 

 days. Prof. Stroobant notes two cases of apparent 

 rapid change of light. On August 29 the brightness 

 increased 0-7 mag. in twelve minutes ; on October 6 it 

 fell 03 mag. in five minutes. Changes like this need 

 verification from more than one station to make sure 

 that they are not due to a local variation in the trans- 

 parency of the air. 



The position and parallax were obtained by observa- 

 tions with the meridian circle. Screens of muslin 

 were placed over the object glass for the brichter 

 stars. The thickest screen reduces the light bv 



