378 



KNOWLEDGE. 



October. 1911. 



to the base of the stratosphere, however hii^'li that 



mav be. 



\\ ind changes are a second most important 



element in passing from the troposphere to the 



stratosphere, es- 

 pecially as to 

 \elocity. \t times 

 this is extreme. 

 Thus at Ditcham. 

 July 2Sth, 1908, it 

 fell from over fortv- 

 hve miles an hour 

 to about six miles. 

 Three days later, 

 however, from over 

 sevent}- miles, the 

 drop \vas onl\- to 

 fifty-eight miles. 

 The stratosphere, 

 therefore, is com- 

 paratively a region 

 of calm as well as 

 of even tempera- 

 ture. This appears 

 to continue at least 

 up to fifteen miles. 

 r>ut at some higher 

 point there is a 

 re\erse change. 

 To dust from the 

 Krakatoa Eruption. 

 in 1883. was as- 

 >igned an initial 

 height of about 

 thirty miles. At 

 this height, which 

 is just double that 



explored by recent investigations, was found over the 



equator an east wind that carried the dust with a 



velocit\- of some seventy to eighty miles per hour. 



At a height of about hfty miles the long enduring 



streak from the meteor seen on Februarv 22nd. 1908. 



tra%-elled with \clocities up to and o\'er one 



hundred miles an hour. 



We must not forget that the assumed extent of 



the Earth's atmosphere, some two hundred miles. 



is at least fourfold this heit;ht. Its densitv still 



A't' //;c courti'sy oj His Majesty's Stationery ( >^//< 



Figure 7. Dines" Balloon 

 Meteorograph. 



suffices to raise meteors to white heat, by friction, 

 up to about one hundred miles. 



Observations at Potsdam indicate that, with a 

 mean surface velocit\- of twelve miles an hour, the 

 speed is seventy-five per cent, greater at a height 

 of five hundred feet, and a hundred per cent., or 

 doubled, at rather over the mile. It is trebled at 

 about two miles, and abo\'e three miles rises to 

 over fifty miles an hour. Up to fifteen hundred 

 feet the \'elocity almost alwa\s increases, but it 

 frecjuentlv falls off higher than this, especialh" 

 with South-east winds. The velocitv just below the 

 stratosphere may exceed twn hundred miles per 

 hour. 



The interest and imj>ortance of the unexpected 



Fig r RE S. 



H. R. Mill, n.Sc. 

 Vl'me^' Box Kite. 



results detailed 

 ing upon them 

 valuable discov 

 ence. But wh 

 indicate that. 

 Biologv. the ac 

 of Upper Air 

 decade of the 

 long to stand 

 achievements. 



above must be the excuse for dwell- 



at such length, so that other verv 



eries must remain without refer- 



at has now been said suffices to 



;is in the case of Mendelism and 



\ances of Meteorology in the region 



exploration during the opening 



twentieth century are destined 



in the foremost ranks of scientific 



MKTEOROLOGiCAL PHOTOGRAPHS. 



The United States Weather Bureau is forming, in its hbrary at 

 Washington, a collection of meteorological photographs, and 

 will welcome additions there to from all parts of the world. 

 The following classes of pictures are among those desired : 

 1 . Views of meteorological offices, observatories and stations. 

 Pictures of meteorological apparatus. 

 Portraits of meteorologists: views of their homes and 



birthplaces. 

 Views showing the effects of storms, inundations, freezes, 



heavy snowfall and so on. 

 Cloud photographs. 



Photographs of optical phenomena (rainbows, halos, 

 Brocken spectre, mirage and so on). 

 7. Photographs of lightning and its effects. 



2. 

 3. 



4. 

 6, 



S. Photographs of meteorologically interesting pictures in 

 old books, or of early prints and paintings. 'e.g.. contempor- 

 ary pictures of the damage wrought bv the Great Storm of 

 1703, in England.) 



Persons who are willing to present such pictures to the 

 Weather Bureau, or who will fiu'nish them in exchange for 

 Weather Bureau publications, are requested to address : 

 Chief C S. Weather Bureau. 

 (Library.! Washington. D. C. 



It will add much to the value of these pictures if the sender 

 will kindly note on the back of each as much pertinent inform- 

 ation as practicable. On picture of classes 4-7, inclusive, 

 should be stated at least the date, hour, and place at which 

 each picture was taken, and the direction toward which the 

 camera was pointed. 



