THE SMITHSONIAN" INSTITUTION. 191 



and dry bulb thermometers, and a set for the calculation of heights by 

 the barometer, will be prepared. 



We may also mention, in connexion with this subject, that a series 

 of preliminary experiments have been made, in the laboratory of this 

 Institution, for the purpose of constructing, from direct observation, a 

 scale of boiling temperatures, corresponding to different degrees of 

 rarefaction of the air. With a thermometer, each degree of which 

 occupies one inch in length of the scale, the variations of the boiling 

 point corresponding to a slight change in altitude are found to be more 

 perceptible than those in the length of the barometrical column. 



A series of experiments has also been made for testing the perform- 

 ance of the aneroid barometer under extremes of atmospheric pressure. 

 The instrument, as usually constructed, has not been found, from these 

 experiments, very reliable, though it may be improved, and thus serve 

 as an indicator of minute atmospheric changes. T think, however, it 

 will not answer for the determination of changes of atmospheric pres- 

 sure of considerable magnitude. 



For the better comprehending the relative position of the several 

 places of observation, now. embraced in our system of meteorology, an 

 outline map of North America has been constructed by Prof. Foreman. 

 This map is intended also to be used for presenting the successive 

 phases of the sky over the whole country, at different points of time, as 

 far as reported; and we have been waiting for its completion, to com- 

 mence a series of investigations, with the materials now on hand, rela- 

 tive to the progress of storms. 



A valuable collection of returns relatiye to the aurora has been re- 

 ceived, in accordance with the special instructions which we have 

 issued for the observation of this interesting phenomenon. These are 

 to be placed in the hands of Captain Lefroy, of the Toronto Observa- 

 tory, and incorporated with observations of a similar kind which lie 

 has collected in the British possessions of North America. An account 

 in full of the whole series will be presented by Captain Lefroy, to be 

 published in the Smithsonian Contributions. 



The meteorological correspondence is under the charge of Professor 

 Foreman. This is found not only to involve considerable labor in the 

 way of arranging the regular returns and sending the required blanks 

 and directions, but also in the discussion of questions on almost every 

 branch of science propounded by the meteorological observers, which 

 we think it our duty in all cases to treat with respect, and to answer to 

 the best of our knowledge. 



'er 



Researches, Sfc. 



Explorations. — The programme of organization contemplates the insti- 

 tution of researches in Natural History, Geology, &c; and, though the 

 state of the funds would permit of little being done in this line, yet we 

 have made a beginning. Besides the assistance rendered to the explo- 

 ration of the botany of New Mexico, by the purchase of sets of plants 

 from Mr. Wright and Mr. Fendler, as mentioned in my last report, a 

 small sum was appropriated to defray the cost of transportation of the 

 articles which might be collected by Mr. Thaddeus Culbertson, in the 



