Hourly Meteorological Observations. 145 



be recorded in the fourth column, should not be placed in a 

 hall or passage where it is exposed to a draught or current of 

 air. 



5. The best electrometer is Bonnet's gold-leaf electrometer. 

 The observations with it should be made in an open field, at a 

 distance from trees and chimneys, Besides the tension of the 

 electricity, as indicated by the extent of the divergence of the 

 gold leaves, it is of importance to ascertain at what height 

 above the soil it first becomes sensible, and in what space of 

 time it acquires a fresh charge, after being touched by the finger 

 or by a piece of metal. The galvanometer may be employed in 

 these observations, as explained in this Number, p. 150. In 

 the observations made in the Royal Observatory at Halle, on 

 the 17th July, by Professor Gartz, Dr Weber, and Mr 

 Hugel, an electrometer was employed, consisting of a gold- 

 leaf freely suspended between two of Zamboni's columns, which 

 could be placed at different distances, so that a lesser oragreater 

 electrical force is necessary to move the gold-leaf, the nature 

 of the electricity being determined by the leaf approaching to 

 the column which had its positive or negative pole turned to- 

 wards it. The electric force was measured by the distance of 

 the Zambonic column which moved it. — See this Journal, No. 

 vii. p. 124-127. 



6. In order to observe the hygrometrical state of the air, 

 cover the bulb of a thermometer with a piece of muslin or soft 

 paper, and having wetted the bulb thus covered, observe, by 

 comparing it with another thermometer, the descent of the 

 mercury arising from the cold produced by evaporation. If 

 the dry thermometer, for example, stands at 50°, and the wet 

 one at 45°, the difference of these indications, or 5°, is the 

 number to be inserted in the appropriate column. Observa- 

 tions with Saussure's and DanielPs hygrometer would also be 

 desirable. — See this Journal, No. vii. p. 127. 



7. If rain should fall, the quantity of it may be measured 

 without a rain-gauge, merely by exposing a circular vessel to the 

 shower, measuring the diameter of its aperture, and noting the 

 depth of rain in inches, if the vessel is equally cylindrical, or 

 the weight of the rain, if the lower part of the vessel is of an 

 irregular shape. 



VOL. VI. NO. I. JAN. 1827- tf 



