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Description of an Automatic 



One of the peculiarities of this method is, that we can 

 print our results at any number of places, provided we have 

 telegraphic communication. One standard barometer may 

 be made to record its indications at fifty different points at 

 the same instant. 



This method may be employed for measuring the fall of 

 rain, and the results can be printed to thousandths of inches 

 every hour, or as often as it is desirable. The general plan 

 will be to receive the rain in a glass siphon containing 

 mercury. One leg of the siphon may be inserted in a 

 brass tube of uniform diameter, of 3 feet in height. Let 

 us suppose that the mercury stands three inches high in 

 each leg of the siphon. If water be poured in the brass tube, 

 the mercury will of course rise in the short leg, and may 

 be made to support a float with machinery precisely simi- 

 lar to that used for the barometer. The area of the 

 vessel receiving the rain can be such that the mercury in 

 rising will measure the amount of rain fallen in decimal 

 parts of an inch. When the water is drawn off, the ma- 

 chine will of itself come back to the zero. If desirable, 

 the apparatus for carrying ten can be so modified that it 

 shall only act in one direction, viz. when the mercury is 

 rising in the short leg ; in this case, we would, at the end 

 of every month, have the total amount of rain fallen, and 

 the same for the year. This form would probably be pre- 

 ferable, because when the water is drawn off, if any 

 quantity should remain in the tube, it would have no 

 effect on the accuracy of the results. 



In applying this principle to the registration of the tem- 

 perature, we would use a simple metallic thermometer. 

 A motion of two or three inches for 100 degrees Centi- 

 grade is amply sufficient to measure with certainty tenths 

 of a degree. After having determined the scale of the in- 

 strument, it becomes an easy matter to adapt mechanism 

 which shall print the results in degrees and decimals, 



