June 2, 1910] 



NATURE 



m 



made at Blue Hill Observatory. These data are par- 

 ticularly valuable for such a study, since in each flight 

 continuous records of temperature, pressure, humidity, 

 wind-velocity and direction were obtained for all heights 

 reached by the uppermost kite, below which the meteoro- 

 4«raph is attached to the wire. In the kite meteorograph 

 used, the thermometer and the hair-hygrometer are screened 

 as much as is possible, thus rendering the heat received 

 from radiation a negligible amount. 



A total of sixty-four kite flights were found in which 

 the meteorograph penetrated a cloud, and, since in six of 

 these flights two cloud-sheets were encountered, the 

 temperature conditions in seventy cloud-strata were obtained 

 as a basis for the investigation. Of these, 63 per cent, 

 showed a rise in temperature of 30'' F. or more in the 

 upper part of the cloud or inamediately above it, 23 per 

 cent, showed no apparent effect of the cloud on the tempera- 

 ture conditions, 7 per cent, showed an inversion below the 

 base of the cloud, while the remaining 7 per cent, showed 

 an isothermal condition prevailing from the base to the 

 summit of the cloud. The flights in which the records 



I I 



Fig. I. — Curve of November 3, 1904, showing increase of temperature 

 occurring within and above cloud. 



were obtained were distributed with fair uniformity 

 throughout tiie year, and the clouds encountered represent 

 all kinds except cirrus and cirro-stratus, these having rarely 

 been penetrated. Moreover, although by far the greater 

 number of flights were made in the da3rtime, many flights 

 at night are included. 



In the largest of the four groups, namely, the one 

 including the flights which showed a rise in temperature 

 in the upper part of the cloud or immediately above it, 

 the increase usually began about half-way between the 

 base and the summit, and persisted until the maximum 

 temperature for the inversion was reached a short distance 

 above the uppermost part of the cloud. Beyond that point 

 the usual rate of decrease, approximately the adiabatic 

 rate for dry air, prevailed as high as the kite ascended. 

 In the next largest group, that including flights in which 

 the cloud had no apparent effect on the temperature con- 

 ditions recorded, a fairly regular rate of decrease, some- 

 what similar to the adiabatic rate for saturated air, was 

 found. In the next group, that including cases in each of 

 which there was an inversion below the cloud, the increase 

 in temperature persisted throughout the cloud and to various 



heights above it, where a decrease again began. In every 

 one of these cases there were the characteristic cyclonic 

 conditions of a shallow easterly wind at the ground over- 

 laid by a warm south-west wind, with precipitation follow- 

 ing. It is thus evident that the increase in temperature 

 was caused by the importation of relatively warm air, 

 and hence began at a height independent of the cloud, the 

 latter only reinforcing the larger warming. In the smallest 

 group, that including the five cases in which there was 

 a practically isothermal condition throughout the cloud, 

 the distinguishing characteristic was really that of the 

 largest group, for, since the usual condition in the lower 

 free air is that of a fairly uniform decrease of tempera- 

 ture approaching the adiabatic rate for dry air, an 

 isothermal state is theoretically equivalent to an increase 

 of temperature with increasing height, such as characterise 

 the cases of the first group. If this be granted, 70 per cent, 

 of the instances show an increase of temperature in the 

 upper part of the cloud and beyond for a short distance. 



This phenomenon of an increase of temperature is 

 entirely independent of the difference in the adiabatic rates 

 of dry and of saturated air, that for the latter being about 

 one-half that of the former. The marked decrease in 



Mfma 



Fig. 2. — Carve of April 4, '905, showing increase of temperature 

 beginning below cloud. 



relative humidity almost always occurring just above a 

 cloud is probably simply the result of the increased 

 temperature. Dr. Shaw, the director of the English 

 Meteorological OfiBce, in discussing the thermal relations 

 of floating clouds, saj's : — " A floating cloud, a finite mass 

 of air carrying water particles, is losing by radiation 

 into space (at night) through the clear air above it more 

 heat than it receives from the earth beneath ; the water 

 globules will, in consequence of this loss of heat, evaporate, 

 and the cloud will vanish " (Quarterly Journal of the Royal 

 Meteorological Society, vol. xxviii., 122, p. 95). It is also 

 worthy of note that in a balloon voyage made in Germany 

 recently, not only was there noted a " warming above the 

 cloud, or at least above the lowest plane of formation," 

 but an increased temperature was recorded in a stratum 

 of ordinary haze (Elias and Field, Quarterly Journal of the 

 Rojal Meteorological Society, vol. xxxi., 134, p. 125). 



Andrew H. Palmer. 

 Blue Hill Observatory, Hyde Park, Mass., May 5. 



Eddy Formation — A Correction. 

 Is Prof. Brjan's solution of the problems in eddy 

 formation (Nature, February 3, p. 408) no mention is 

 made of the fact that a vortex in one plane at rest, when 

 the method of conformal representation is used, does not 

 in general lead to a solution in which the corresponding 

 vortex is at rest. 



NO. 21 18, VOL. 8 {] 



