May, 1916. With, Perhaps, a Shght Upward Curve at Either Extremit

MAY,1916. MONTHLY WEATHER REVIEW. 245 TABLE!?.-Vi~por pressure at pyrhelhetric slationa on hys when solnr TABLE3.-Daily totals and departures of solar and dy radiation during radiatwn inteidies ‘were meammi. May, 1916--Continued. [Gram-cabrias per square cantimeter 01 horizontal 8urha.l Washington, D. C. 11 Madison, Wls. 11 Lincoln, Nebr. Santa Fe, N. Mex. II I I: 8s p.~Date. a :. p:m.ll Date. a.m. p.m. ‘ Day of month. ------1916. Mm. Mm. 1916. Mm. Mm. 1916. Mm. Mm. 1916. Mm. Mm. Wash- mdi- Ltny 1 7.3 7.87 May5 6.27 7.57 May 1 4.17 4.57 May 4 3.15 2.39 ington. son. 6 9.47 818 7 en 224 3 4.93 4.57 12 3.88 416 9 5.36 6.50 11 4.57 4.17 4 5.36 650 13 3.15 1.S -- 10 7.M 12.21 18 4.37 4.57 5 6.76 7.57 15 1.96 1. 12 1916. Gr..eal. Gr.-eot. Qr.-cal. 12 4.57 7.57 31 5.56 9.83 6 0.47 ai8 10 1.7s I.!&? May 21...... 162 -304 - 10 218 17 5.36 4.37 7 10.97 1429 18 345 287 n...... 13 -193 231 18 6.50 5.36 8 6.02 5.16 19 300 1.96 23...... 537 69 -558 so0 19 4.75 as0 10 4.95 449 23 2.87 3.63 ?A...... 448 - 21 -834 279 a0 7.04 7.67 17 6.02 5.56 29 4.57 11.81 25 ...... 621 I 419 - 51 -710 228 21 4.95 5.56 22 9.14 1229 25 4.17 8.81 26 ...... 636 6ae 140 59 -570 287 25 1313 13.13 23 8.81 1861 28 3.81 363 27 ...... 581 621 85 - 17 -485 270 26 9.47 10.59 29 14.10 16.79 27 287 4.17 as ...... 53.1 570 39 193 -44tl 463 28 16.20 lam 25 10.97 ILSQ 29 3.30 300 29 ...... 452 662 - 42 -239 -4.38 !a24 28 10.59 la21 30 ...... 267 731 -227 249 -715 473 30 io.% 10.97 31 ...... 637 33s 144 130 -571 803 - Decade departure...... I...... -341 81 On the mornings of 29 the readings ...... -4,057 +I28 obtained at Santa Fe steady atmosplienc ...... -7.9 +D.3 conditions throughout the half- eriods. Reduced to .. , mean solar distance of the estrapolated to zero : /‘ :, . &- -7 I, ’ . ,#’- ’ , air mnss they give solar radiation intensities of 1.76, 1.79, . . CIBCUMHOBIZONTAL ABC’OBSSSWD. and 1.77, res ectively. Employing the vapor pressures JULIANT. Assistant Observer. given by Tab e 2 in a pl to the above measurements By GRAY, the Smi‘thsonianY “A%riGf procedure for determining [Dnted: Weather Ihmau, Cincinnati, Ohio, June 13, 1916.] approximately the value of the solar constant”,1 we ob- 011 June 5, 1916, while observing a very bright solar tain 139, 1.91, and 1.88, respective1 , or values but halo of the ordinary type, a phenomenon was noticed slightly lower than Abbot’s mean v airue for the solar which at htwas believed to be the lower portion of the coiistant . great halo of 46’. The arc was 30’ or more in extent, Skvlieht polarization measurements at Washington on concave to the sun, and so situated that its middle point six diyigide a mean of 51 per cent, with a maxi&um of appeared vertically beneath the sun. It was also re- 58 er cent onMa 19. markable for its vivid colors, and in this characteristic it ‘fable 3 shows t3: at at Washington there was a defici- bore a strong resemblance to the “circumzenithal arc,” ency in the total radiation received during the month an example of which the writer observed at Ludington, amounting to 3.7 per cent of the normal. At Madison Mich., during the winter of 1913-14. there was an excess amounting to 4.2 per cent. Since the The fact was at once noticed that the arc ap eared flat, htof the year the deficiency at Washington is 7.9 per i. e., not having that degree of curvature whicR would be cent of the average amount, and at Madison the excess is expected of a halo of 46”, and it was not concentric with 0.3 per cent. the halo of 22’. So far as we are able to judge, the arc TABLE3.-Daily totals and departures of solar and sky radiutio,r during was parallel to the horizon at an altitude of about 20°, May, 1916. with, perhaps, a shght upward curve at either extremit . [Gram-csiorh per square centimeter of horizontal surIace.1 It therefore seems reasonably evident that we had to & with the “circumhorizontal arc” or “lower tangent arc of the halo of 46’,” concerning which Besson says, “So Departures Daily totals. from normal. far, only three or four observations of this arc are known.” Day of month. - “he henomenon remained visible for about 15 minutes after iscove from 12:50 to about 1:05 p. m. (90th Wssh- Madl- Lin- WSSh- Wash- Madl- d! ington.1 son. I coln. ngton. Lngton. son. Meridian timxrDuring this eriod the sky was every- - -- where visibly covered with tE in cirrus or cirro-stratus 1916. Gr.Cal. lffr.sol. OT.-COl. 9r.Cal. ffr.Cal &.sal. &.sal. clouds in whch numerous white streaks and patches ap- Yay 1...... 590 237 739 110 -217 110 -217 a ...... 335 547 353 -157 92 -47 -125 peared. We endeavored to make such measurements as 3 ...... 531 300 R7 46 -96 - 1 -221 4 ...... 394 550 676 -94 93 - 95 -1% were ossible without instrumental equipment, which, 5 ...... 534 e58 692 44 m - 51 72 thoug! lacking in that degree of accuracy which would be ci ...... ciaa 299 sra 130 -210 79 -138 7 ...... 231 uu9 596 -aaz 210 -183 R desirable, are presented with the belief that the possible s ...... 544 704 703 50 244 -133 316 limits of error in either direction are such that the results Y ...... 6M) 578 559 105 118 -&I 434 10 ...... 495 468 716 -1 8 -29 442 obtained may be of some value. 11 ...... 510 762 ’ 294 23 301 -6 743 A piece of cardboard in which a pin was stuck perpen- 12 ...... w 365 88 147 - 76 141 Bli7 dicularly at the end of a black line served as a sort of 13 ...... !a2244 85 -216 -217 - 75 450 14...... 169 133 157 -329 -329 -4lM 1-21 sextant, by means of which our measurements were made. 15 ...... 595 668 535 BB a08 -308 327 10 ...... 22s asl 607 -ni -m -579 125 The angles were plotted on the cardboard and measured 17 ...... 514 834 838 15 170 -564 ass with a protractor. The measurement was taken in each 18 ...... 4(10 690 376 -39 228 -6n3 521 19 ...... 711 538 179 213 13 -390 594 case from a point as near the middle of the band or ribbon 20 ...... 658 394 190 100 - 72 -230 52a of light as could well be judged. Decade departure...... -1...... -mi BO The radius of the ordinary halo as measured was ex- actly 223’, which, considered as a check, may indicate 1 AnMh Of the Astrophyslcd Observatory ol the Smithsol m Institution, Washing- ton, 1% 2115. that the other measurements made by the sanie method

Unauthenticated | Downloaded 10/02/21 09:44 PM UTC 246 MONTHLY WEATHER REVIEW. MAY,1916 are approximately correct. The solar distance of the arc liness of the lens surfaces, elimination of lens or camera at 1 p. m. was measured at 46)’, while the altitude of the glare, dan er of diffraction with small apertures, etc.- sun at the same hour two days later was 66’. The sun’s C. P. B[utfw].

altitude at the moment considered must have been be- 5 -/* > I- -/ tween 65’ and 63’, where, according to the theory of PROPAGATION OF SOUND IN THE ATMOSPHERE.’ Bravais, the solar distance of this arc should be between 46’ and 47’. (See “Different forms of Halos and their By E. VAN EVERDINGEN. Observation,” MONTHLYWEATHEE REVIEW, July, 1914.) [Rcprin#ed/ran Science Abtnrcts, Sect. A, A&. 25, 1918, 3 458.1 In various investigations on the propagation overfeat distances of sounds from intense sources, specia y 111 THE BLUE OF TEE SKY AND AVOGADRO’S CONSTANT.’ the case of volcanic eruptions and explosions, deviations By D. PACINI. have been found, partly regular,gartly irregular. The source of sound is always surroun ed by an area of regu- [Rcpdntcdfrom ScIenee Abtraets, Sect. A, Mar. ‘25, 1918, &?&3.] lar or irregular shape, where the sound is hoard every- Rayleigh’s theory attributes the blue of the sky to where, but the source is far from being always situated molecular dispersion; but we have also to do with dust symmetrically within this area, and the dimensions of the and with molecular ag lomerations (on ions, on uncharged latter are not even in the first place determined by the nudei produced by ta e action of ultra-violet light on intensity of the sound. In many cases a second area of oxygen, or on water va or) which are larger in size than audibility occurs, se arated from the first by a region t,he dimensions require (P by Rayleigh’s theory, but which where no sound at aY 1 is heard. Sometimes this second vary in size and number. The author has studied ob- area art1 surrounds the first; sometimes it consists on1 served de artures from the inverse fourth-power law, and of is0YZ ate spots. It can be said generally that the smad tabulate Bthe calculated value of n. in A*. It is mostly est distance from the source of sound for this second area numerically smaller than 4, but has been found as large is usually much more than 100 kilometers and that the as 7. The observations are reduced to a series of typical intensity of sound at this smallest distance is no less curves, less or more in disaccord with the theoretical than at the outer border of the first area of audibility, curve, and the probable causes of these discrepancies are which is much nearer to the source of sound. These considered. A erfect atmosphere would give data cor- facts are illustrated by diagrams of seven different cases responding to a\ out 62 x loZa molecules per gram-mole- which have previously been investi ated. These are as cule; the author fmds his observations lead to a value of follows: (1) Explosion of 15,000 kif ograms of dynamite 57~102~.Dember, found by analogous methods 25, at Farde, in Westphalen, December 14, 1903 [G. von der Abbot and Fowle 52, and King 62.3, ~10~~.On the Borne, Abs. 106 (1911)l; (2) explosion of 25,000 kilo- whole, this is sufficient to show that the blue of the sky ams of dynamite near the Jungfrau Railway Novem- is mainly due to molecular dispersion.-A. D[aniea]. gr15, 1908 (A. de Quervain); (3) three eruptions of the volcano Asama in Japan on December 7, 1900, December q7: *, ’./ ; 25, 1910, and April of gunpowder and d PHOTOGRAPHY OF ZODIACAL LIGHT AND COUNTERGLOW.* F’upwhara); (5) exp By A. E. Douo~nss. powder in a magazine at 1912 [J. N. Diirr, Abs. 1295 (1914)l. [i?eprhted /rom 8dence Abtraets, Sect. A, Apr. 25, 1918, 424.1 Two chief lines have been followed in the endeavor to e lain these facts. The first way, now quite old, as- cn”% es the abnormal propagation of sound to the influence of variations in temperature and wind velocity in the superposed layers of air in the atmosphere. It is easy to see how, by certain suppositions about the vertical distri- bution of wind velocit , the peculiarities of the propagation of sound, s ecia6 y the silent region, may be ex- plained. The inli uence of temperature, which decreases upward, is a decrease of the velocit of sound in the higher regions, thus causing the sounJ raTs to curve upward from the earth. A horizontal wind in the direction of the sound, and with higher velocities at higher levels, may counteract the above temperature effect and over- come it, so turning the rays down again to the earth. A silent region followed by a second audible area is thus accounted for. The second and entirel different line of thou ht was put forward by Von der some. He supposes tf at the appearance of silent regions, in some cases at least, may be due to the change in composition of the atmosphere, which is caused by the unequal decrease of the partial pressures of the constituents of the atmosphere. If no mixing by convection currents occurred, each of the gas- eous constituents of the atmosphere would form an atruos- phere entirely awording to its own laws. In consequence * Proc., K. had. Amsterdam, 1916,8,l8933460.

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