were deduced the following tables, published in the Monthly Weather II and 14 km.; this is the “ thermal zone ” as discovered and so Rev1ew:- called by him.

Mean Temperature Gradient; in degrees Fahrenheit per 1000 ft. ' Winter -S pring. Summer. Autumn.

e from the ground up to the respeqiwe altitudes' Altitude' Dec., Jan., Feb. Mar., Apl., May. June, July, Aug. Sept., Oct., Nov. St t. I0O0' 1500 2000 3000 4000 5000 6000a

°”S' ft. ft. ft. ft. ft. ft. ft. Km- °C- °C. °C- °C.

O °- o O 0 Ground -}- 1-9 -l- 5-1 +13-0 + 7-5

° ° 0-5 + 1-4 + 4'7 +13-6 + 7-7

Wash1nton, D.C . 5-6 4-4 4'0 3-5 3-2 3-o 3-1 1-o - 0-2 + 2-4 +11-8 + 6-1 Cairo, lll 9-7 6-6 6-o 4-9 4-7 4-3 - - 1-5 - o-2 + 0 1 9-7 + 4-0 Cincinnati, O. 13-o 6-3 6-9 5-8 5-6 4-7 4-2 2-o - 1-4 - 2 1 7-3 ~l- 2-2 Fort Smith, Ark. 7-2 7-0 6-7 5-8 3-8 - - 2-5 - 3-7 - 4-3 5-0 + 0-4 Knoxville, Tenn. 8-4 6-2 6-6 5-4 5-0 A - - 3-0 - 6-0 - 6-4 2-1 - 1-7 Memphis, Tenn. 7-8 6-8 5-o 3-8 3-7 3-5 - 3-5 - 8-7 - 9-3 + 0-2 - 4-2 Springfield, Ill. 7-6 5~7 5-1 4-4 '4'0 3-7 3-6 4-o -10-9 -I2°2 - 2-7 - 6-5 Cleveland, O. 5-7 4-1 3-6 3-5 4-1 4-1 4-3 4-5 -14-52 -15-2 .- 5-3 - 9-3 Duluth, Minn. 5-2 4-8 4-6 4-6 4-3 3-8 4-6 5-0 -17-0 -18-5 - 8-3 -I2'4 Lansing, Mich. 7-5 6-o 4-7 4-1 3-9 3-8 - 6-0 -23-7 -25-2 -14-8 -18-7 Sault Ste Marie, Mich. 6-6 6-2 5-2 4-5 3-9 3-0 - 7-0 -31-5 -32-0 -21 -7 -25-8 Dodge, Kans .... 6-3 5-2 4-8 3-7 3-1 3-2 3-2 8-0 -39-0 -39-0 -29-3 -33-5 Dubuque, Iowa 6-9 5-9 4-6 3-5 3-2 3-3 — 9-0 -46-9 -46-7 -38-o -41-4 North Platte, Neb. . 6-8 6-5 5-9 5-2 4-4 4-7 5-4 ro-o -54-6 -52-7 45-3 -48-3 0}11al12l.N€b- - ~ * 5'4 4'9 3'6 3'2 3'5 3'3 Il°0 "57'9 -53'5 50'3 "54'4 f Pierre, S. Dak. 5-9 5-1 4-8 4-3 3-7 4-4 4-0 12-0 -57-9 -53 1 52-7 -57-1 Topeka, Kans. 7-4 6-2 4-9 4-0 3-8 3-9 4-5 13-0 -56-9 -52 2 51-5 -57-1 14'0 "55'5 '52'5 *5I'3 'f57'I,

Average 7-4 5-8 5-2 4-4 4-0 3-8 4'I

It is evident that the annual average vertical gradient of tempera-Altitude, Temperature, ture over Paris is between 4° and 6° C. per 1000 metres of Stations ascent in the free air, agreeing closely with the value 5° per 1000 F 6611- Gfadlellll R€dL1Cf10I1- metres, which has come into extensive use since the year 1890, on the recommendation and authority of Hann, for the reduction of ° F- ° F- land observations to sea-level. The winter gradients are less than Washington 210 -3-00 *I5'2 those for summer, ossibly owing to the influence of the condensa-Cairo; - 315 “4'30 -25'6 tion into cloud and) rain during the winter season in France; the Cincinnati . 940 5'I5 "27'5 same value may not result from observations in the United States, F011 Smith 527?? where the clouds and precipitation of winter do not so greatly Krl0XVill0 - 990 -5'00 -2I°5 exceed those of summer. The work at Trappes is therefore not Memphis - 319 3'50 -17'3 necessarily representative of the general average of the northern Springfield . 684 -~3~85 -I7'7 hemisphere, but belongs to a coastal region in which during the Cleve and - 705 -4'I0 -I8'8 summer time, at great heights, the air is cooler than in the winter Duluth - - - 1197 ”'4'30 -I7'6 time, since during the latter season there is an extensive flow of Lansing . . 869 -3-85 -I7'0 warm south winds from the ocean over the cold east winds from Sault Ste Marie 722 *-3'4»5 -I5'7 the land. Sounding balloons have also been used elsewhere with Dodge . . 2473 -4~IO '~II'6 great success. The greatest heights attained by them have been Dubuque 894 -3-30 -I4'5 25, 89 metres at Uccle, Belgium, on the 5th of September 1907, N01'tl'l Platte ~ ' 2311 -5'40 -I3'3 ani? 25,800 metres at Strassburg, August 1905. Omaha 1241 -3'20 -'I2'9 The most extensive meteorological explorations of the free Pleffe ~ - 1595 3'90 l4'4 atmosphere have been those accomplished in Germany by Richard Topeka 4 972, -3'33 “I6'5 Assmann and Arthur Berson, beginning (1887) in co-operation with In this table the second column gives the altitude of the ground at the reel on which the kite wire was wound. The third column shows the average gradient in degrees Fahrenheit er 1000 ft. between the reel at the respective stations, and a uniflhrm altitude 5280 ft. above sea-level. The fourth column shows the total reduction to be applied to the temperature at the reel in order to obtain the temperature at the I m. level above sea. These gradients and reductions are based upon observations made only the German Verein for the Promotion of Aeronautics and the Aeronautic Section of the German Army, afterwards under the auspices of the Prussian Meteorological OHice, but later as a wholly independent institution at Lindenberg. All the details of the work during 1887-1889 and the scientific results of seventy balloon voyages were published in three large volumes, Wissenschaftliche Luftschijfahrten (Berlin, 1900). The work done at Tegel at the Aeronautical Observatory of the Berlin Meteorological Office, the 1st of October 1899 to April 1905, was published in three volumes The great work of L. Teisserenc de Bort began with 1897, when a new independent establishment, the during the six warm months from Ma to October 1898. 4 of Ergebnisse. But the location at Tegel had to be given up and The kite-work at the Blue Hill Ohservatory has been

published in full in the successive Annals of the Annual Temperatures and Wind. Harvard College Observatory, beginning with 1897, -vol. xlii It has been discussed especia ly by H. H. Tegel, 1903, Tegel, 1904. Lindenberg, 1905. Lindenberg, 1905, Clayton with reference to special meteorological - » Phenomena, such as areas of high and low pressure, -Altitude. Days °C -Days. °C. Days. °C. Days. Metrespersee air and cloudy weather, the winds and their G1-01100 565 9-2 366 365 8-5 365 4-65 velocities at different elevations, insulation, radi- 500 m 355 67 364 365 6-2 362 8-65 ation, &c., and has served as a stimulus and model ' 1,000, , 344 4-3 361 352 4-0 356 8-85 for European meteorologists. Kite-work has also I'5OQ H 252 2-0 279 294 2-6 306 8-55 been successfully prosecuted at Trappes, Hamburg, 2,000 H 170 0.0 186 242 0.5 257 9 5 Berlin, St Petersburg, and many other European 2'5OO H 93 -1-8 132 - 179 1-1 195 10-o stations. The highest flights that have been attained 3,000 H 55 5 9 79 - 1 19 2-8 127 10-7 have been about 8000 metres.

he founded his private observatory at Trappes near Paris devoted to the problems of dynamic meteorology. His results are published in full in the Memoirs of the Central Meteorological Bureau of France for 1897 and subsequent years. Beginning with the sounding balloons devised by Hermite, he subsequently added kite work a s supplementary to these. In the COWIPIES rendus (1904), he gives the mean temperatures as they result from five years of work, 1899-1903, at Trappes. Out of 581 ascensions of sounding balloons there were 1411 that attained 14 km. or more, and the following table gives the average temperatures recorded in these ascensions. It will be seen that there is a slow decrease in temperate up to 2 km.; a rapid decrease thence up to 10 km., and a slow decrease, almost a stationary temperature, between Royal Prussian Aeron:-futic

Observatory, " was founded at Lindenberg, under the direction of Dr Assmann, who has published the results of his work in annual volumes of the Ergebnisse of that institution, considering it as a continuation of the work done at Berlin and Tegel. In addition to these elaborate official publications various summaries have been published, the most instructive of which is the chart embodying daily observations .with corresponding isotherms at all attainable altitudes, published monthly since January 1903 in Das Weller. The growtlh of this aerial work and the reliability of the results may be inferred from a statement of the number of ascensions madeeach year: 1899,6; 1900, 39; 1901, 169; 1902,261; 1903, 481; 1905, 513. This large number, combined with 581 voyages of

Teisserenc de Bort at Trappes and many others made in England,