August 31, 1916] 



NATURE 



DO 



machine is started and run on the new surface with 

 a gradually increasing load until about 4000 to 6000 

 tons per yard of width have rolled over it; this is 

 called the consolidation period. The test proper is 

 then commenced, and the machine is rup at a rate of 

 about 2200 tons per yard of width per hour. In most 

 cases with good materials a well-laid surface remains 

 smooth and polished until about 200,000 tons per yard 

 of width have rolled over it. About this stage wave- 

 like markings begin to appear; these gradually extend 

 until at 400,000 tons the surface becomes consider- 

 ably waved and the vibration is excessive. The test 

 is then considered complete. The results of four tests 

 with mexphalte and aztecphalte are included, and are 

 of interest as showing that considerable difference in 

 the durability may be caused by the method of laying 

 nd by the workmen employed. 



We have received a booklet entitled "Economical 

 Dishes for War-time," by Miss Florence A. George 

 (Messrs. Cornish Bros., Birmingham, price 6d.). It 

 contains a number of useful recipes for the preparation 

 of economical meat and vegetable dishes and sweets. 

 A brief introduction deals with the food requirements 

 of the body, and at the end some hints are given on 

 ';;e management of gas-stoves. 



The following books are in the press for inclusion 

 in the "Cambridge Technical Series" of the Cam- 

 "' ridge University Press : — " Experimental Building 

 science," vol. i., J. Leask Manson ; '"Alternating Cur- 

 rents," W. H. N. James; "Development of English 

 Building Construction," C. F. Innocent; "Naval 

 Architecture," J. E. Steele; "Chemistr}' and Tech- 

 nology of Oils and Fats," F. E. Weston and P. J. 

 Fryer; "Physics for Engineers," J. Paley Yorke; 

 "Chemistry of Dyeing," Dr. L. L. Lloyd and M. Fort. 



OUR ASTRONOMICAL COLUMN. 



Bright Display of Auror.a Bore.\lis on August 27. 

 — A fine exhibition of Aurora Borealis was 

 observed by Mr. W. F. Denning at Bristol 

 in the early morning of Sunday, August 27, 

 between the hours of 2 and 4 G.Sl.T. Shafts of 

 light were first observed at about 2h. 15m. ascending 

 amongst the stars of Ursa Major and Draco, and 

 reaching considerable altitudes. Changes affected the 

 appearances at short intervals, the streamers would 

 fade away and new ones form, while the invariable 

 disposition of the \\hole was to move quickly from 

 the west to the east side of the north point. Some 

 of the more conspicuous streamers were particularly 

 recorded as they passed over certain stars, and the 

 mean rate of motion across Ursa Major was found 

 to be 15° in three minutes. 



The active region seemed to extend from as nearly 

 as possible N.W. to N.E., but the N.W. and N. 

 showed the greatest abundance of streamers ; in the 

 N.X.E. there was a succession of faint bands of light 

 rising upwards to the left of Auriga. Many of the 

 rays observed in the X. region could be faintly traced 

 to altitudes of 70°. The phenomenon was watched 

 until 3.45, when the sky had regained its normal ap- 

 pearance, and twilight had become strong in the north- 

 east. 



DlSTRIBLT^ION OF THE PoLES OF PLANETARY OrBITS. — 



Prof. H. C. Plummer recently found that the mean 

 pole of the orbits of the minor planets was situated 

 at a distance of 53' from the pole of the ecliptic, in 

 longitude 16-7°, and he was led to investigate Its 

 relation to the poles of the major planets (Monthly 



NO. 2444, VOL. 97] 



Notices, R.A.S., vol. Ixxvi., p. 378). A diagram show- 

 ing the relative positions of the poles revealed several 

 features of interest, to which no special attention had 

 previously been directed. It thus appeared : (i) that 

 the poles lie three by three on five lines; (2) that the 

 pole of each orbit, with the exception of Neptune, lies 

 on two of these five lines ; (3) that each line contains 

 the orbital poles of two adjacent major planets. Prof. 

 Plummer found it difficult to believe that this was 

 merely a chance arrangement. Prof. J. B. Dale has. 

 since directed attention to further interesting features 

 of the polar diagram (Roy. Ast Soc., June). On 

 measuring the inclinations of the five lines to the line 

 drawn from the pole of the ecliptic in the direction 

 315°, he obtained the following results: — 



(i) Earth — Mars — Mercury, 3° = 82° -79°. 



(2) Earth — Uranus — Venus, 3i°=82°-5i°, 



(3) Uranus — Jupiter — Saturn, 82° =82°. 



(4) Mars — Jupiter— Neptune, 136° = 82 '^ + 54°. 



(5) Mercury — Venus — Saturn, i6i° = 82° + 79°. 



The directions of the five lines can thus be expressed 

 very closely by the formulae, o, o±2)3, a±3l8, where 

 0=82° and )8 = 26^°. 



The diagram also shows that there are several pairs 

 of lines joining poles which are nearly parallel. 1 here 

 is apparently nothing in the theory of the secular per- 

 turbations of the nodes and inclinations of the 

 planetary orbits which would lead to the expectation 

 of such definite relations, or to the continuance of 

 these relations if they did exist at a given time, but 

 Prof. Dale considers it almost incredible that iht 

 should be purely accidental. He inclines to the view 

 that these remarkable relations may indicate the action 

 of other forces, such as might be due to a resisting 

 medium, in addition to the gravitational forces. 



Solar Variability. — For the more precise study of 

 the distribution of radiation of different wave-lengths 

 across the sun's disc, the obser\^ing station of the 

 Smithsonian Institution at Mount Wilson has been 

 provided with a tower telescope having a concave 

 mirror of 12-in. aperture and 75-ft. focal length. A 

 description of this instrument, together with some of 

 the observational results for 1913 and 1914, has been 

 given by Messrs. Abbot, Fowle, and Aldrich (Smith- 

 sonian Miscell. Collections, vol. Ixvi., No. 5). Spectro- 

 bolometric measurements were made at seven different 

 wave-lengths, namely, 3737, 4265, 5062, 5955, 6702,, 

 8580, and 10,080. The new results agree cjosely with 

 those obtained at Washington in 1907, so fai as the 

 two series are comparable, and the curves of intensitv 

 distribution show in a ven.- striking way the greater 

 uniformity of the light across the disc as the wave- 

 length increases. There 'were, however, slight, but 

 significant, differences between the mean results 

 for different years, a greater contrast of 

 brightness between the centre and edge occurring 

 in 1907 and 1914.. as compared with 1913, taken as a 

 standard ; that is, in years when the solar constant 

 was high the solar contrast was greater than usual. 

 Besides the long-period change, there were small 

 changes of contrast from day to day, correlated with 

 short-period fluctuations of solar radiation ; for this 

 type of variation increase of solar radiation was 

 attended by decrease in the contrast between the edge 

 and centre of the disc. The authors are thus led to 

 consider that there are two causes of change existing 

 in the sun : (i) the increased effective solar tempera- 

 ture accompanying high solar activity*-, producing in- 

 creased radiation and increased contrast ; (2) the vary- 

 ing transparency of the outer solar envelopes from 

 day to day, increased transparency resulting in in- 

 creased radiation but decreased contrast. 



