PORTABLE METEOROLOGICAL STATION. 355 



In these papers criticism has been a secondary feature. Mere criticism is of 

 very little account. Unless a^man can do more than that he had better not say 

 anything. In all of these papers the attempt has been to instruct, to throw light 

 upon a subject of great interest, which from peculiar circumstances — want of 

 general facts — long remained in darkness. Criticism of the " weather prophet " 

 system has only been introduced as auxiliary to this instruction. In the past 

 such a system, if it may be so honored, was excusable, but its days are past and 

 any further continuation of this " system " is the merest farce, too simple for in- 

 telligent persons to regard with the least favor. It is not to be depended upon ; 

 is not reliable and is generally unworthy of the attention of intelligent people. 



Washington, D. C, August 22, 1881. 



PORTABLE METEOROLOGICAL STATION. 



Under this name is designated an instrument especially adapted for the use 

 of travelers in mountain excursions in order that they may be able to observe 

 and accurately register the different atmospheric 'phenomena they experience, 

 and so fill the gap that generally exists in the history of Alpine and other as- 

 censions. 



This instrument is so arranged that it can, in any place, conveniently and 

 exactly determine the most important meteorological phenomena, the pressure 

 and temperature of the air, and its degree of humidity. It is a combination of a 

 barometer, thermometer, hygrometer, and compass, arranged in a small case that 

 can easily be carried, as it weighs one kilogramme. 



The different parts are so perfectly balanced that the instrument can be used 

 in any position and can stand, without injury, the rough usage of mountain trav- 

 eling. 



The barometer is the aneroid, a well-known instrument, and is especially 

 adapted to show the pressure of the atmosphere, and the elevation of the place of 

 observation above the sea level. 



The temperature is shown by a mercurial thermometer, fixed on a copper 

 tube, that forms a general support for the whole apparatus. The thermometer 

 registers the centigrade system from 25° below zero to 40° above. 



The degree of humidity in the atmosphere is determined by a Saussure hair 

 hygrometer, which is slightly modified in this apparatus. A well constructed hair 

 hygrometer gives results sufficiently accurate for general meteorological observa- 

 tions, as the hairs work regularly, and their small bulk causes them to be easily 

 affected by the surrounding air, which is a great advantage when there are only 

 a few moments to make an observation. 



This hygrometer is the only one available for, those altitudes where the tem- 

 perature is below zero, and where, consequently, ^neither the psychrometer nor 

 the condensing hygrometer could be used. 



