36 



NA TURE 



[May io, 1906 



is effected in the following manner. The balloon is 

 only partially filled with gas, and is then securely tied 

 up. As it rises the external pressure is lessened and 

 the gas inside expands, until finally the rubber is no 

 longer able to stand the strain and the balloon bursts. 

 A small parachute is used to prevent a too rapid fall of 

 the meteorograph, and sometimes a second smaller 

 balloon, filled to a less extent, so that it does not burst, 

 is also attached ; the second balloon takes the place of 

 the parachute, but is employed that it may float over 

 the position of the fallen meteorograph," and direct 

 attention to it. With paper balloons an automatic 

 arrangement is used by which the balloon is freed when 

 it reaches a certain height. The general result is 

 that the meteorograph returns to the earth within a 

 time of about an hour, and within a distance of a 

 hundred miles from the starting point. 



Observations obtained by the help of kites have the 

 advantage of being less costly, but they are dependent 

 on the weather conditions, and it is' not often that 

 heights exceeding two miles are reached. At Linden- 

 berg in Germany, the best equipped station for the 

 purpose in existence, last year a height of just on 

 four miles was reached by a train of kites. Given 

 sufficient wind it is a perfectly simple process to send 

 a kite up to the height of a few' thousand feet, although 

 if the wind be very strong it is not so simple to draw 

 it back again. The chief obstacle to attaining great 

 altitudes is the wind resistance upon the cord or'wire 

 which holds the kite, and it is on this account that 

 the strongest and thinnest obtainable steel wire is 

 used. _ The wire introduces many technical difiiculties ; 

 it is difficult and to some extent dangerous to handle, 

 and although capable of withstanding a great strain 

 if fairly used, if a kink is once formed the piece of 

 wire in which it is, is utterly useless. Usually steel 

 music wire, the kind of wire'usedin a piano in fact, 

 of about i-32in. in diameter is used; this will bear 

 a weight of 2Solbs., and weighs i61bs. to the mile. 

 With a good kite presenting 77 square feet of surface 

 to the wind and 8000 feet of this wire, a vertical 

 height of one mile is easily reached under favourable 

 conditions of wind, and one kite of this size has 

 carried a meteorograph to 8000 feet of height. The 

 conditions are not always favourable; instead of a 

 steady wind of twenty-five to thirty miles per hour, 

 increasing somewhat with altitude, which affords the 

 bes.- conditions, it not infrequently happens that quite 

 different velocities are found in different strata. It is 

 impossible to get through a stratum in which the 

 velocity is under fifteen miles per hour, and if a 

 velocity of much over fortv miles per hour is en- 

 countered in the lower strata", the kite is very likely to 

 be damaged or the wire broken. At greater heights 

 a_ higher Velocity is not so likely to cause damage, 

 since the air is less dense, and (a'point of perhaps far 

 greater importance) the wind is far steadier. 



Hence it is easily seen that to reach very great 

 heights with a train of kites, in addition to" haying 

 apparatus of the best design and quality, exceptional 

 weather conditions must hold, and the observer must 

 succeed in straining his wire just short, but only just 

 short, of its breaking point. The attempt very often 

 ends in the breaking of the wire near the winch, 

 and the departure of five or six miles of wire and six 

 or eight kites. 



Very interesting results have been given by the un- 

 manned balloons. It has been found that when they 

 have reached a great height they fall in some locality 

 lying to the east of their starting point, not neces- 

 sarily due east, but on a more easterly meridian. 

 Since they pass far beyond the upper limit of the 

 cirrus cloud, this fact confirms the statement that in 

 the temperate l;ititudcs the upper currents are always 

 NO. 1906, VOL. 74] 



from some westerly point. M. Teisserenc de Bort 

 also finds that balloons sent up in a cyclone tend to 

 move away from the centre at great heights, thus 

 showing that the cyclonic circulation is not a mere 

 surface phenomenon. He also states that at ten miles 

 height the air is warmer over the cyclone, and colder 

 over the anticyclone. 



When observations by means of kites were first 

 started by Mr. Rotch, a't Blue Hill, Boston, U.S., it 

 was hoped that the long disputed point as to the origin 

 of cyclones would be elucidated; so far this has not 

 been the case. 



Ferrel, the well-known American meteorologist, 

 held that cyclones were convectional effects, and that 

 they were maintained chiefly by the latent heat of con- 

 densation of the vapour in the central and rainy part. 

 Dr. Hann on the other hand considers that cyclones 

 are what may be described as driven eddies in the 

 general circulation of the atmosphere. Opinion on the 

 Continent, based on the results of observations ob- 

 tained by balloons and kites, seems to be in favour of 

 Dr. Hann's hypothesis, but Mr. Clayton, of Blue Hill, 

 U.S., considers that the ascents there made favour the 

 convectional theory. The results of some two hundred 

 kite ascents which I have obtained in England and 

 Scotland, with an average height of about one mile,, 

 seem to me to give no evidence one way or the other. 

 I think, however, that a fundamental error has gener- 

 ally been assumed in the discussion. We know that 

 in a gas in equilibrium under a conservative system 

 of forces the isothermal and isobaric surfaces must 

 be identical ; this point at least is not open to question. 

 It is not, therefore, the proper test to consider whether 

 the temperature in a cyclone is greater or less than 

 in an anticyclone at the same height, but the test is 

 whether it be greater or less at points on the same 

 isobaric surfaces ; and the isobaric surfaces in 

 temperate latitudes may well differ from surfaces of 

 equal height above mean sea level by a thousand feet 

 or more. W. H. Dines. 



THE BICENTENARY CELEBRATION OF THE 



BIRTH OF BENJAMIN FRANKLIN. 

 ^p HE oldest scientific society in the new world is, I 

 i believe, the American Philosophical Society of 

 Philadelphia. The Society was founded by Benjamin 

 Franklin, son of an English father and born at 

 Boston, Massachusetts, in January, 1706. It was 

 natural that the bicentenary of the birth of a man of 

 such extraordinary and diverse genius as Franklin 

 should be commemorated in his native land, and 

 accordingly during the past winter the Society issued 

 invitations to leading universities and societies through- 

 out the world to be present, through their delegates, 

 at a festival to be held at Philadelphia from April 17 to 

 20. The date of the meeting was no doubt chosen 

 because Philadelphia is liable to be intolerably hot in 

 the summer, and would certainly be deserted at that 

 season bv manv of the leading members of the Society, 

 vet the chosen time was not a good one for European 

 delegates, since academic duties would certainly pre- 

 clude any large attendance from across the seas. 

 Although, then, there were actually present only some 

 half-dozen delegates from Europe, yet many European 

 societies were represented by honorary members of 

 American nationality, and sent addresses of congratu- 

 lation to the Philosophical Society. The United States 

 and Canada were naturally in great force, and the 

 hundred and fifty or two hundred delegates who 

 attended formed an imposing body of men of scientific 

 repute. 



The proceedings began on the evening 6f April 17, 



