February 19, 1920] 



NATURE 



675 



Is Venus Cloud-covered? — Mr. Evershed has 

 taken many photographs of the sf>ectrum of Venus in 

 recent years, for the purpose {inter alia) of endeavour- 

 ing to detect the Einstein shift, and of testing his own 

 hypothesis that the earth has an effect on the atmo- 

 spheric circulation of the sun. In the course of this 

 worlc he found, to his surprise, that a much longer 

 exposure-time was needed than was the case in photo- 

 graphing the spectrum of a cumulus cloud on which 

 the sun was shining (Monthly Notices»R.A.S., Novem- 

 l)er). Mr. Evershed expected the time to be shorter, 

 for the intensity of sunlight on Venus is 192 times as 

 great as on the earth. Allowing for the absorption of 

 \'enus's atmosphere, he concludes that if Venus were 

 covered with clouds similar to our cumulus clouds, 

 the exposure-time would be less on the former than 

 on the latter in the ratio of i to 1-3, whereas the 

 contrary is the case. He concludes that the atmo- 

 sphere of Venus is not cloud-laden, but that its lower 

 strata contain much dust in suspjension, veiling the 

 surface features. This conclusion is similar to that 

 rt'ached bv Prof. Lowell from his observations at 

 Flagstaff. 



Mr. Evershed thinks that the values of the colour- 

 indices assigned by Prof. H. N. Russell to the sun 

 and Venus ( + oygm. and +o-78m.) are mutuallv in- 

 consistent, since they imply that no selective absorp- 

 tion takes place in Venus's atmosphere. Mr. Ever- 

 shed finds evidence of decided selective absorption in 

 the violet, as compared with his cloud spectra. 



PROFESSIONAL METEOROLOGY. 



CIX parts of the new Professional Notes of the 

 --' Meteorological Office have now been issued. The 

 first ' deals with the relation between cloud and wind 

 direction at Richmond, and gives tables for each month 

 for loh., i6h., and 22h. for fifteen years, showing the 

 number of times each cloud amount was associated 

 with each wind direction or with calms ; it would 

 perhaps have been clearer if percentage values had 

 been given. Several important points come out, such 

 as the well-known tendency of cloud to disperse at 

 night, but it is also shown that this tendency is not 

 the same for all winds or for all seasons. Cloud fore- 

 casting became important during the war, and will 

 in future be of wide application; it is to be hoped, 

 therefore, that Lieut, (now Capt.) Brunt will fulfil his 

 intention of continuing this research. Tables also give 

 values for Greenwich for January and Julv, and 

 various differences from Richmond are apparent; 

 Richmond had only 59 calms in 180 months, while 

 Creenwich had 58 in 20 months, which indicates, 

 perhaps, a difference in estimating light v^-inds. 

 Greenwich had more south-west and fewer south and 

 north-west winds than Richmond, due probablv to 

 local exposure. 



It would be more satisfactory to compare cloud 

 amount with wind at cloud-level or with gradient 

 direction, for Mr. Newnham's paper ° on a night vallev 

 wind shows that surface winds mav be shallow and 

 more or less unrelated to upper-air phenomena. Cold 

 air flows down valleys at night in radiation weather, 

 and if, at so open a station as Benson, the wind at 

 night sorpetimes blows "very steadilv from eost-bv- 

 south to east-south-east regardless of what the direc- 

 tion had been during the previous dav." the need for 

 caution in dealing with surface winds is obvious. But 

 in the case of fog it is the surface wind that is of 



* "On the Inter-relation of Wind Direction and C'lo-id Annnnt at Rich- 

 inopH." Bv T.ieut. David Rrunt. fMeteoroIo^iral Oni-e. loiS.) Price ■;(/. 



2 " Notes on Examples of Katabatic Wind in the Valley of the Upper 

 Thames at t'le Aeroloeical Obs-rvatory of the Meteorol'igical Office at 

 Kenson. Oxon." By E. V. Newnham. (Meteorological Office, 1918. ) 

 I'rice 3'i'. 



importance, as appears in Mr. Brooks's paper ^ on 

 the fog in London on January 31, 1918, when the 

 incidence of the fog seems to have been influenced 

 by " shallow streams of cold air flowing down the 

 sides of hills." The isobaric maps in this paper show 

 a bend in the isobars over the Thames estuarv which 

 Mr. Brooks thinks is real, but possibly exaggerated 

 "by slight inaccuracies in some of the barometer 

 readings. " Those who draw isobars know how peculiar 

 are some of the readings, and would welcome a future 

 Professional Note on these peculiarities. 



A vast amount of information was obtained during 

 the war on upper-air temperatures and winds, and it 

 would be a real loss to meteorology if this were un- 

 used or lost. Lieut. Stacey and Capt. Chapman are 

 therefore to be congratulated on having made use of 

 some of these records. Lieut. Stacey' deals with 

 upper-air temperatures at Martlesharri Heath from 

 February, 1917, to January, 1918, and sets out the 

 information clearly on the whole, though several mis- 

 prints are noticeable. Unfortunately, "no informa- 

 tion is to hand of the type and exposure of the instru- 

 ments used," which is to be regretted, espcciallv as 

 one wojid .suppose such information could have been 

 obtained; as a matter of fact, the thermometers were 

 exposed on the wing-struts of the aeroplanes, but the 

 tvpe of thermometer varied from time to time, and 

 therefore the early records are probablv not strictiv 

 comparable with the late ones; but these facts are 

 not recorded in the paper. It is very desirable that 

 all details of meteorological war-work should be col- 

 lected before it is too late to obtain them. 



Capt. Chapman ' reviews formulae connecting in- 

 crease of wind velocity with height. Manv of the 

 earlv ones were linear, but linear formulae are un- 

 likelv, and were probablv onlv intended as working 

 guides until more observations were available. From 

 a consideration of manv observations, including iqo in 

 north-eastern France, the author deduces the formula 

 V = (7!ogH-f6 (where V is the wind velocity. H the 

 height, and a and h are constants), which fits most 

 of the observations below the height at which the 

 mean gradient velocity is reached. The whole paper 

 deserves careful studv. In another publication " Capt. 

 Chanman discusses the normal curve of errors in con- 

 nection with what meteorological observations should 

 be classified as unusual or exceptional. 



Meteorology has advanced raoidiv in recent vears. 

 and these publications, and others, show that the 

 advance in this countrv is due largelv to the Meteoro- 

 lo£>ical Office, and it is to be honed that its fijture 

 activities may not be hampered bv the proverbially 

 unscientific attitude of Government Departments. 



STEAM BOILERS AND ECONOMISERS. 



A S chief engineer of the Manchester Steam Users' 

 -'"^ -Association Mr. C. E. Stromeyer prepares a 

 yearly memorandum. The memorandum for the vear 

 iqi8-iq deals with fuel economv and with economiser 

 and furnace collapses. Some industries require much 

 power and little steam for heating and boiling; 

 others much steam and little power. If two such 

 industries could combine, the cost of i h.p. could be 

 reduced from, say, 2 lb. of coal to J lb. If, for 

 instance, a spinning mill consumes 20 tons of coal 



' "Incidence of Fog in I-ondon on January 31, 1918." By C. E. P. 

 Brooks. (MeteoroloEiical Office. tqi8.) Price 3'/. 



■* "Upper-4ir Temperatures at Martlesham Heath. Februarv, 1917, to 

 January, T918." By Lieut. W. ¥. Stacey. (Meteorological Office, 1919.) 

 Price i.f. 



5 "The Varia'ion of Wind Velocity with Height." By Capt. E. H. 

 Chapman. (Meteorological * tffice, 1019.) Price ij. 



5 ''On the Use of the Normal Curve of Errors in Classifying Observation* 

 in Meteorology." By Cart. E. H. Chapman. (Meteorological Office, loiq. 

 Price 6./. 



NO. 2625, VOL. 104] 



