SCIENCE— SUPPLEMENT 



to possible dangea- on liis left, to his left reaa:, 

 and to his right. It is well known th-at the left 

 hand side of the street should be used by pedes- 

 triajis when itihere is no sidewalk. ' ' 



There is a very real and important problem 

 with respect to the ideal eonstruotion of a traffic 

 sign. How many words would be read in the 

 available time? What would be the minimum 

 sdze of letters? Whart; should be the structure, 

 place, color and content of signs? He contends 

 thia,t there is already a body of practical expeii- 

 ence and scienitifie information available which 

 would only need to be adapited to highway use 

 and experimentally justified. 



For instance, he said, it has been tilioroughly 

 demonstrated (that adults do not read famiHar 

 words letter by leitter but by familiiar letter 

 groups. Yet, here in Waishington, we have signs 

 reading ' ' Slo. ' ' Dr. Dodge said thajt when he 

 first saw that sltnange sign it took him many 

 times the effort and time io understand and inter- 

 pret it that would liave been sufficient for 

 "Slow." 



"The nature and time of hand and arm sig- 

 nals by automobile drivers should be also regu- 

 lated. They are sometimes short, and sometimes 

 long, sometimes early and sometimes late. The 

 continuous indioatiom of a driver's intentions be- 

 ginning at least five seconds before a movement 

 is executed and cont±iiuing until a movement is 

 completed would be a great advantage. ' ' 



Traffic policemen should wear white sashes and 

 trolley posts should be painted in alternate bands 

 of white and black to increase their optical use- 

 fulness. 



PREDICTS WINTER WEATHER BY SUMMER- 

 TIME TEMPERATURES 



Science Service 



Forecasting the rainfall for the coming winter 

 and spring from the past summer's ocean tem- 

 peratures, Dr. Geo. F. McEwen has predicted that 

 the Southern California coastal region wUl receive 

 about one half: iaeh less than its average rainfall 

 during the season 1922-23. He suggested the pos- 

 sibility of applying the same system to predic- 

 tions over more extensive areas. Dr. MeEwen is 

 neither a goose-bone prophet nor a crystal gazer, 

 but the oeeanographer connected with the Soripps 

 Institution for Biological Research. He bases his 

 system of forecasts on carefully worked out ob- 

 servations during the last six years. 



These observations show that when the ocean 

 temperature averages colder than usual the rain- 

 fall is heavier than usual and when the summer 

 seas are warmer than the average the subsequent 



rainfall is smaller than the average rainfall. A 

 fall of one degree in teonperature corresponds on 

 the average to an increase of about two inches in 

 the rainfall. 



Eadnfall in the Southern California coastal re- 

 gion depends mainly upon the fl.ow of the mois- 

 ture-laden ail- from rthe Pacific and is propor- 

 tional to the amount of the air transferred. 



This in turn depends on the formation of a belt 

 of high air pressure over the conitdnent, he ex- 

 plains. In summer the barometric pressure is 

 greater over the oean than the land for two 

 reasons. The wind velocity over the smooth 

 Water surface averages two or three times as 

 great as that over the relatively uneven land and 

 in summer the air flows from the land. But as 

 the season advances to winter, air flows over tie 

 land from the wateir and carries a great mass of 

 ladr from the Pacific Ocean to the North Amer- 

 ican, continent. 



Enough pressure measurements over the Nonth 

 Pacific on which to base predictions being un- 

 available. Dr. McEwen used the known relation 

 between pressures and surface ocean tempera- 

 tures. The velocity of the winds which move 

 clock wise over the Pacific depends on the air 

 pressure and the upweHing of cold bottom wateof 

 along the -coast and therefore the rate of cooling 

 of the surface water is proportional to the wind 

 velocity. The lower the ocean temperature at oi 

 near the surface during the late summer and 

 autumn, he declares, the greater must be the in- 

 tensity of the ocean belt of high air pressure and 

 accordingly the greater will be the expected sea- 

 sonal rainfall over the coastal region of Southern 

 California. 



When asked wMch days would be the rainy 

 ones, Dr. Ewen explained that long range fore- 

 oai^ting is only done at the sacrifice of details and 

 for daily information he advised waiting for the 

 regular government forecast issued twenty-four 

 to forty-eight hours in advance. 



Another example of successful long range fore- 

 casting is the prediction of the monsoon rainfall 

 of India, months in advance, by means of ob- 

 servations on atmospheric pressure distributions 

 over vast areas of land and water. 



ECLIPSE EXPEDITIONS IN AUSTRALIA 



By Isabel M. Lewis, U. S. Naval Observatory 

 Science Service 



Nevek have eclipse expeditions been favored 

 "with fairer skies than spread over the entire con- 

 tinent of Australia on the eventHul day of the 

 total solar eclipse of last September. From 



