472 THIRD REPOllT l8So. 



the mean temperature of the air and the ground. — Detached 

 observations on this subject will be useful, but a continued and 

 regular series of results for each locality will be more valuable'. 

 (See Report, vol. i. p. 224.) 



7. That series of comparative experiments should be made on 

 the temperature of the dew-point, and the indications of the 

 wet-bulb hygrometer, and that the theory of this instrument 

 should be further investigated. (See i?^/;or/, vol. i. p. 243 — 246.) 



8. That particular attention be paid to the improvement of 

 the instruments of meteorological research. 



9. That Mr. Phillips, and Mr. Wm. Gray, jun,, be requested 

 to undertake a series of observations on the comparative quan- 

 tities of rain falling on the top of the great tower of York Min- 

 ster, and on the ground near its base ; and that similar obser- 

 vations be instituted at other places^. 



A standing Committee was appointed, consisting of Profes- 

 sors Airy, Christie, and Forbes, Dr. Dalton, Dr. Robinson, Mr. 

 Potter, and Mr. Scoi'esby, to draw up instructions^ for ob- 

 serving Auroras, and to endeavour to estabhsh corresponding 

 observations in every part of the kingdom. 



Desiderata noticed in Prof. Forbes s Report, 



1. Verification of Dr. Dalton's theory of the constitution of 

 the atmosphere, by direct experiment. {Report, vol. i. p. 206 ; 

 Phil. Trans. 1826.) 



2. Experiments in various latitudes upon the temperature of 

 the earth at moderate depths, by means of thermometers with 

 long tubes ; with a view to determine the position of the " in- 

 variable stratum," where external causes cease to produce any 

 effect. {Report, vol. i. p. 221.) 



^ The height of the springs may be determined with sufficient accuracy by a 

 common portable barometer. 



^ The observations at York have been made at three adjacent stations of 

 known height, with gauges made on the same mould, and measured by one gra- 

 duated glass vessel : tliej' have been continued from the 1st of February 1832 

 to the present time. From the results, it has been inferred by Mr. Phillips 

 that the diminution in the quantity of rain, at the higher stations, has a certain 

 constant dependence on the height of the station, and on the condition of the 

 air as to moisture in the different periods of the year. For the further elucida- 

 tion of this subject, it is desirable that experiments upon the same plan should 

 be tried in other situations, and especially where the climate is of a different 

 character from that of York ; in the humid atmosphere of Cornwall, for exam- 

 ple, and in the drier air of the midland counties. Gauges exactly similar to 

 those in use at York will be supplied from thence to persons undertaking to try 

 these experiments, on application to the Secretaries. 



3 An abstract of the directions which have been drawn up by the Committee, 

 is given in the Appendix. 



I 



