172 



METEOROLOGY. 



Meteorolo- 



Plan of a Meteorological Journal. 



Advanta- In examining meteorological tables, the difficulty of 

 ges of the perceiving at once the extent of the fluctuations that 

 take place in the temperature and pressure of the at- 

 mosphere is a frequent and just subject of complaint ; 

 and to remove this difficulty, a very simple expedient 

 has been proposed, and is now frequently adopted. 

 Fig. 10. This uaethod is represented in Fig. 10, where the 

 horizontal lines denote the degrees of the thermome- 

 ter, and the spaces between the vertical lines repre- 

 sent the days of the month. The extreme elevations 

 and depressions of the instrument, or the points at 

 which it stands at the hours of observation for every 

 day, are marked on the diagram, and the line joining 

 these points exhibits at one view the fluctuations of 

 temperature. A similar diagram is employed to re- 

 present the elevations and depressions of the barome- 



ter. The necessity of this method however is, in some 

 measure at least, superseded by entering in a separate 

 column, as in the above plan, the daily range of both 

 instruments. That of the thermometer is found by 

 subtracting the maximum from the minimum, and an 

 approximation to that of the barometer, by taking the 

 difference between the observations at 10 morning and 

 evening of the same day, which is entered in the 7th 

 or 8th column, according as the mercury has risen or 

 fallen, and also the difference between the observations 

 at 10 on the evening of the one day and 10 on the 

 morning of the following day, which is entered in the 

 9th or 1 Oth column. The sum of these two differen- 

 ces is then carried to the last column, as the amount 

 of the barometrical range for the whole twenty.four 

 hours. 



Plan con- 

 tinued. 



Exten ^ e part'C"^ 18 ln tne above plan, whicli, as far as 



of ihe'plan. we know, are not to be found in any other table yet 

 ' made public, are the results of Anderson's formula, 

 as already explained, viz. the point of deposition, or 

 the temperature at which the atmosphere would begin 

 to deposit moisture ; the actual quantity of moisture 

 contained in 100 cubic inches of air, expressed in de- 

 cimals of a grain ; and the relative humidity, or quan- 

 tity of moisture expressed in hundredths of what would 

 produce complete saturation. In addition to these, 

 however, it would be desirable, we think, to ascertain 

 the following facts. 



1st, The lowest point to which the temperature of 

 the ground sinks during the night, and which might 

 be found by exposing a minimum thermometer on the 

 grass, and recording the result in the morning ; and 



2dly, The greatest depression of the hygrometer, 

 both at the surface of the ground and a few feet above 

 it, which might be ascertained by the self-registering 

 hygrometer formerly explained. Were these instru- 

 ments generally employed, every meteorological jour- 

 nal would exhibit a series of experiments, which could- 

 hardly fail both to give greater precision to the dis- 

 coveries that have already been made, and to extend 



