173 Meteorological Journal. 



The barometer employed in the preceding observations, was 

 made by John Newman of London, and is similar to that of the 

 Royal Society of London. The inner diameter of the tube is .55 

 inch, and the tube plunges into a cylindrical glass vessel about 

 three inches in diameter nearly filled with quicksilver. The scale 

 is movable, and terminates at its lower extremity in an ivory 

 point, which by a screw may be brought to exact contact with the 

 surface of the mercury in the cistern. The scale is graduated to 

 half hundredths of an inch, and read by a vernier to the two thou- 

 sandth part of an inch. After the instrument was completed, I 

 directed' it to be taken to the apartments of the Royal Society, 

 and placed by the side of the Society's barometer, where it was 

 left for a day, in order that both might acquire the same tempera- 

 ture. The two instruments were then read off alternately by 

 myself and Mr. Roberton, the assistant secretary of the Society. 

 The mean of observations at four different times, made my barom- 

 eter .012 inch lower than the flint glass barometer of the Royal 

 Society. The instrument is rendered portable by inverting, and 

 turning a screw in the bottom of the cistern. It was admirably 

 packed on springs, and I have reason to believe suffered not the 

 slightest injury from transportation. The height of the barome- 

 eter cistern above tide water at Albany, is believed, to be 1131 

 feet. The correction for capillarity is assumed to be .006 inch, 

 and that for temperature is made by Schumacher's Tables, Co- 

 penhagen, 1826. 



The thermometers are all graduated by Fahrenheit's scale. 

 The external thermometer is divided to fifths of a degree. It is 

 exposed on the north side of the building where there is a per- 

 fectly free circulation of air. It is on a level with the barometer 

 cistern, and 21 feet from the ground. The wet bulb hygrometer 

 is a common thermometer whose bulb is enveloped in a white 

 cotton rag, and kept wet by means of another rag hanging from 

 a vessel of water by its side. When the water freezes the in- 

 strument is not observed. Daniell's hygrometer is of the usual 

 construction, and was made by Newman. At each observation, 

 the point at which the dew disappears, as well as that at which 

 it forms, is invariably noted and the mean taken. 



The vane is attached firmly to an upright revolving shaft, to 

 whose lower extremity is secured a graduated circle. The zero 

 of this circle indicates the South point of the compass j 90'^ is 



