INVESTIGATION OF TEMPERATURE CHANGES. 225 



a tenth in a century. This would be only one whole degree of variation in 

 n. thousand years ! " * 



Arago finally concludes that, by extending the thermometric comparison 

 from 1776 to 1852, there would be instrumental evidence of an increase of tem- 

 perature to the amount of one-tenth of a degree, and he remarks as follows : 

 " Thus, instead of a diminution of tetnperature at Paris, we seem to have 

 made out a slight increase [nous serious arrives a un leger rechauffenient]. 

 However, these observations would have to be continued for at least half 

 a century longer before we could say with certainty that this tenth of a 

 degree of which I have just spoken is not an irregular and accidental 

 oscillation." 



The result indicated by Arago, as he himself admits, is too small in 

 amount and uncertain in character to be accepted as a basis for any gener- 

 alizations; and the same may be said of all the other investigations which 

 have been made by meteorologists in working over the records of tempera- 

 ture observations for the purpose of endeavoring to make out whether proofs 

 of a secular change of climate could be obtained. The general result of 

 these investigations seems clearly to be that no positive change of tempera- 

 ture can be made out as having been instrumentally determined. A few of 

 the most important researches of this kind may here be noticed as proof 

 of the statement just advanced. 



Professors Loomis and Newton investigated the question "■ whether the 

 mean temperature of New Haven, Conn., had changed since the time of the 

 earliest recorded observations." f Their material for this work consisted 

 of more or less fragmentary observations, dating back, nominally, to 1778. 

 There is no proof furnished that the instruments employed were sufficiently 

 corrected for the errors known to be inherent in all thermometers, as men- 

 tioned above, so that any result obtained can hardly be considered as of 

 much value. The authors conclude as follows : " The final result is that the 

 mean temperature of New Haven by the last 45 years, is one-fifth of a 

 degree [Fahrenheit] lower than by the first 41 years; but this quantity does 

 not exceed the probable zero error of most of the thermometers employed 

 in the observations ; and we must conclude that if the mean temperature 



* Arago farther adds : "The two epochs thus compared enilirace between them a period dviring wliieh certain 

 parts of France have been stripped of their forests [fortenient dcboisees]. The mean temperature of Paris has, 

 however, undergone no perceptible change in consequence of this disforesting." 



t See Elias Loomis and H. A. Newton, On the Mean Temperature, and on the Fhictuations of Temperature, 

 at New Haven, Conn., in Transactions of the Connecticut Academy of Arts and Sciences, Vol. I. p. 194. 



