PROFESSOR LOOMIS'S STORM 289 



dertake to pursue this subject further, to observe the effect 

 of the formation of dew on the actinometer, and also, to 

 take into account the latent caloric received in the upper 

 strata of the atmosphere during storms of rain and snow. 



Much may be learned on this subject without an acti- 

 nometer of M. Pouillet's construction, by a continued series 

 of experiments of the following nature. 



Place a thermometer on some bad conductor of caloric 

 the inside of a common washing tub, for example, whose 

 bottom is covered three or four inches thick with straw, or 

 charcoal, or wool, and expose the whole so arranged, on the 

 grocmd under the open sky, free from the radiation of sur- 

 rounding houses, and note from hour to hour every evening, 

 the difference between this thermometer and one swung 

 briskly in the air near the tub. 1 The more the thermometer 

 at rest sinks below the one in motion, the colder will it in- 

 dicate the upper regions of the atmosphere to be ; except 

 when dew is formed; when this takes place, the further 

 depression of the thermometer at rest is greatly diminished 

 by the evolution of latent caloric; and this will frequently 

 happen, when there is no dew formed on the ground round 

 about. 2 



May it riot be possible that the approach of a distant 

 storm might be discovered by this means ? 



The following article appeared in the Philadelphia Sat- 

 urday Courier, of March 18th, 1837. Its value is much 

 increased by Professor Loomis's investigation of the same 

 storm. 



Mr. Editor : On reading in the London papers, recently 

 arrived, the account of the remarkable snow storm that 

 passed over England on the 24th, 25th, and 26th of Decem- 

 ber, my attention was recalled to some circumstances con- 



1 See Pouillet's Elements of Physics and Meteorology, third edition. 



2 If this plan is inconvenient, the thermometer may be laid on the grass, or 

 on a board lying on the ground. 



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