351 



of its occurrence. Data for such conclusions are as yet very insuf- 

 ficient ; they should always, however, form a part of the record at 

 all land stations where registers are kept. 



In order that all observations of the elasticity of the aqueous 

 vapour may be strictly comparable, it is desirable that all should be 

 computed by the same tables ; those founded upon the experiments 

 of MM. Regnault and Magnus may be most suitably recommended 

 for this purpose, not only on their general merits, but also as being 

 likely to be most generally adopted by observers in other coun- 

 tries. 



Temperature of the Air. 



Tables of the mean temperature of the air in the year, and in the 

 different months and seasons of the year, at above 1000 stations on 

 the globe, have recently been computed by Professor Dove, and 

 published under the auspices of the Royal Academy of Sciences 

 at Berlin. This work, which is a true model of the method in 

 which a great body of meteorological facts, collected by different 

 observers and at different times, should be brought together and 

 coordinated, has conducted, as is well known, to conclusions of 

 very considerable importance in their bearing on climatology, and 

 on the general laws of the distribution of heat on the surface of the 

 globe. These tables have, however, been formed exclusively from 

 observations made on land. For the completion of this great 

 work of physical geography, there is yet wanting a similar investi- 

 gation for the oceanic portion ; and this we may hopefully anticipate 

 as likely to be now accomplished by means of the marine observa- 

 tions about to be undertaken. In the case of the temperature of 

 the air, as in that of the atmospheric pressure previously adverted 

 to, the centres of geographical spaces bounded by certain latitudes and 

 longitudes will form points of concentration for observations, which 

 may be made within those spaces, not only by the same but also by 

 different ships ; provided that the system be steadily maintained of 

 employing only instruments which shall have been examined, and 

 their intercomparability ascertained, by a competent and responsible 

 Authority ; and provided that no observations be used but those in 

 which careful attention shall have been given to the precautions 

 which it will be necessary to adopt, for the purpose of obtaining the 

 correct knowledge of the temperature of the external air, amidst the 



VOL. VII. 2 M 



