GREEN UPPER EE GE ON LOW The not infrequent optical phenom- sun's edge. They grew and faded from enon known as the "green flash" was 6:55 47" until about 5 seconds before observed with a small telescope at the the time of disappearance of the up- Blue Hill Observatory on the evenings per limb. No flash was observed on of May 11 and May 16, 1934. this occasion. May 11 was characterized by an By a simple calculation it can be unusual dust storm which reduced seen that the color on May 16 was visibility to 2 or 3 miles until about first observed while the lower edge 6 p.m., when the dust cloud started of the sun's disk was still 27' 26" to lift. Twenty minutes before sun- above the horizon—3 min. 58 sec. set the visibility in the west was ex- before sunset. cellent. The sun was observed through Sunset in both cases was accom- a 4-inch telescope with a terrestrial panied by characteristic distortions eyepiece. While the sun's upper limb of the solar disk. On the 16th, the was still approximately 2' above the upper limb seemed drawn out in a horizon, the rim was seen to be lined straight line for the last 5 or 10 with green, varying in intensity from seconds. instant to instant. The green per- It is very doubtful if the color phe- sisted from the 2' elevation until the nomena on these occasions could have instant of disappearance of the upper been seen with the naked eye. The limb, when it appeared to flash up use of a telescope, as Lord Rayleigh from the horizon 30" or 40"—then has pointed out,1 possibly results in vanished. an increase of spectroscopic resolving On May 16, the time of sunset was power, and certainly increases the ap- observed to be 6:59 45". At 6:55 47", parent size of the luminous source bluish-green was first noted on the up- which makes its color easier to dis- per edge in the form of slivers or tinguish.—R. F. Baker. streaks parallel to the horizon. These 1Lord Rayleigh, Normal Dis- streaks would grow to a maximum in- persion as the cause of the "Green Flash" at Sunset, with Illustrative Experiments. Proc. tensity—then fade out just above the of Roy. Soc., A, vol. 126, 1930. THE ROBERT DECOURCY WARD CLIMATOLOGICAL COLLECTION A reference library in climatology a period of nearly a century by ex- has been assembled in the Institute change with all countries of the world of Geographical Exploration, Harvard this climatographic collection is quite University; and $1000 has been pre- extensive. Climatographic publica- sented by the children and sisters of tions currently received in exchange the late Professor Robert DeCourey by the American Meteorological Soci- Ward to start an endowment for its ety, as well as those continuing to maintenance and growth. The nucleus arrive at Blue Hill and the Astronom- of the collection was Professor Ward's ical Observatory, are being placed in working library, which has been pre- this collection, where, it is believed sented to Harvard University. To this they are most likely to be useful. It group of books, which relate chiefly seems fitting that this fine climato- to general climatology, have been logical collection be named after Pro- added most of the climatographic pub- fessor Robert DeCourey Ward, who lications in the libraries of the Harv- in the course of his 40-odd years of ard College Observatory and the Blue teaching and research in climatology Hill Observatory. Accumulated over at Harvard brought to the United

Unauthenticated | Downloaded 09/24/21 12:15 AM UTC States from Europe the principles of an American school of climatology climatology so well developed there, which has guided governmental and adapted them to American conditions, private climatological work for several and, by example and precept, started decades.—Charles F. Brooks.

AERONAUTICAL NOTES Dispersal of thin cloud or ap- term forecasting, based largely on air- parently by the air-mixing action of mass analysis, is uppermost. At Parks an airplane is described in the July Air College, for example, after a brief and November issues of the Meteor- introduction to meteorology in the ological Magazine, 1935. R. E. Wat- first term, there begins in the fourth son (pp. 140-141) cites the cutting term a systematic course in practical of a lane through an Acu cloud about meteorology, chiefly air-mass analy- 10-12 feet thick to a width slightly sis, including reception of reports, de- beyond the tips of the wings. The coding, map-making and forecasting, clear space lasted 7 minutes. A. E. which runs consecutively for five (p.141) described the splitting terms of 12 weeks each. "The stu- of thin Acu by an air liner, and the dent's grade will depend on the accur- subsequent widening of the space. F. acy with which he predicts the weath- H. Dight (p.232-233) describes how er."— C. F. B. an airplane cut its own fog lane for Barometric altimeters not to be landing at the S. Farnborough aero- trusted in storms.1 When you are fly- drome about a year ago: ing in a fog or at night, just how "Late in the afternoon fog suddenly high are you above the surace? Your began to develop on the aerodrome. I should estimate it was about 15 ft. altimeter may say 1000 feet, but when deep, when an aeroplane came in to was it last set, and how much could land. Actually although lost to view the general atmospheric pressure at the pilot did not land at the first this time and where you now are dif- attempt, but suddenly came up out of the fog, made a half circle of the fer from the pressure at the time and aerodrome and then landed success- place it was set? In the hurricane of fully . . . during the first approach the Sept., 1935, the pressure at Long Key pilot cut a lane in the fog and then fell an inch in four hours, and 0.68 returned to make a perfect landing in this clear lane." in 95 minutes. Since the storm was Mr. Dight suggests that mixing of moving forward only some 30 miles in the foggy air with the drier air above 4 hours, it would have been possible by the propellor probably was respon- had a pilot flown straight toward the sible.—C. F. B. center to have experienced an inch pressure change, representing about Meteorological instruction for avi- 1000 feet of altitude, in less than an ators. While all courses for aviators hour (due allowance being made for have always included instruction in rapid side drift in hurricane wind). meteorology, such study of the me- Flying at "1000 feet," therefore, he dium in which the men were to fly would soon have plunged into the sea. was generally limited to a few weeks' Steep pressure gradients occur else- elementary study of the subject. The where than in tropical cyclones, chief emphasis was on avoidance of though usually they are smaller in clouds, storms, turbulent winds and total amount. At Blue Hill Observa- contrary winds. Now it is interesting to note a much more intensive study 1Cf. L. P. Harrison: Use of altimeter in Aerial Navigation from meteorological stand- of the subject is usual, and that short- point, BULLETIN, Oct. 1935, p. 216.

Unauthenticated | Downloaded 09/24/21 12:15 AM UTC