154 



NA TURE 



[June i8, 1903 



SCIENTIFIC KITE FLYING. 



SYSTEMATIC observations of the temperature and 

 humidity of the upper air have been made for 

 many years past, both in America and on the Continent, 

 kites being the means employed mostly in America, 

 and kites and balloons on the Continent. 



The plan adopted is to send up a kite of some 60 to 

 80 square feet of lifting surface, the line used being 

 steel music wire instead of string, additional kites 

 being attached to the line as occasion requires. The 

 end kite, or the line close to it, carries a self-recording 

 instrument, and in this way observations at a height 

 approximating to or even exceeding three miles are 

 sometimes obtained, although it is not often that the 

 air motion in the various strata is such as to render a 

 height of more than 10,000 feet possible. The obstacle 

 to be overcome is the pressure of the wind upon the 

 line, which soon reduces the angular altitude of the 

 kite, and it is on this account, rather than on the 

 greater strength of steel for the same weight, that 

 steel music wire is preferable to string, the resistance 

 •of the wire on account of its smaller section being so 

 much less. 



by 6 ft. by 



There are few days on which a small elevation may 

 not be reached by a kite, but days really suitable are 

 not plentiful. It is self-evident that a suitable wind is 

 the first requisite, and to obtain a great height a suit- 

 able wind must prevail from the lowest to the highest 

 strata reached. We cannot, of course, alter the wind, 

 but fortunately we are able to move the point to which 

 the kite line is attached, and this practicallv comes to 

 the same thing as altering the force of the wind. The 

 most convenient means of doing this is to fly the kites 

 from the deck of a steam vessel, and during last 

 summer observations were thus obtained for seven 

 weeks almost daily. 



The work was inaugurated by a committee of the 

 Ro3-al Meteorological Society, cooperating with a com- 

 mittee appointed by the British Association. ^ Thev 

 hired a small steam tug of 55 feet length and 14 feet 

 6 inches beam. The vessel was stationed at Crinan, 

 which is at the north end of the Crinan Canal, on the 

 west coast of Scotland, an^. Sundays excepted, kite 



5 See paper on "The Method of Kite-flying from a Steam Vessel, and 

 JWeteorological (Observations obtained thereby off the West Coast of Scot- 

 land {Quarterly Journal of the Royal Meteorological Society, April). 



ascents were made from her deck every day, no matter 

 what the weather, from July 8 to August 26. The 

 vessel could not steam more than seven knots, and 

 the wind velocity necessary to raise a kite is from nine 

 to twelve knots, so that on occasions when it was a 

 dead calm no kite could be started. It happened, how- 

 ever, that no day was calm throughout, so that some 

 time during the hours of daylight the opportunity of 

 reaching at least 1500 feet elevation was afforded. 

 Had the tug been capable of ten instead of seven knots. 

 I have little doubt but that a height of 5000 feet might 

 have been attained every day. 



Using one or two kites only, no difficulty was ex- 

 perienced. The most troublesome point was getting 

 the kite together when the wind was strong. The tug 

 was small, and had no bulwarks, so that there was no 

 shelter of any kind on deck, but her smallness was 

 certainly an advantage in another way. A larger 

 vessel would have produced eddies in the wind, and 

 probably have rendered it difficult to start the kite direct 

 from the deck. As it was we had no trouble, and it 

 was ver}^ seldom that a kite failed to rise steadily from 

 the starting point. In calm weather the vessel was 



^'O- 1755. ^'OL. 68] 



kept steaming against, or nearly against, the wind so 

 as to produce sufficient relative motion to raise and 

 maintain the kites. In rough weather she was taken 

 out against the wind for some ten or twenty miles 

 until a position was attained from which a clear run 

 down the wind was possible, and the kite was then 

 started. A wind of force 5 on the Beaufort scale 

 is the most suitable wind for kite flying. This is known 

 technically as a fresh breeze, and is sufficient to pro- 

 duce a moderate amount of white on the sea surface. 

 One of the kites of the usual size for scientific kite 

 flying will, in such a breeze, exert a pull of about 

 50 lbs. The wire used will bear a strain of some 

 300 lbs., and weighs about 16 lbs. to the mile, so that 

 one kite in such circumstances will take nearly two 

 miles of wire, and, if it be a good one, will raise the 

 instruments to about 5000 or 6000 feet. The pull of 

 50 lbs. is well within the limits of stability of the kites, 

 and is on the whole about the most convenient to work 

 with, if one can be certain of the goodness of the kite. 

 At Crinan the tug was so manoeuvred that a tension 

 of 40 lbs. for each kite on the line might be main- 



