56 J. F. Miller, Esq., on the 



Form, Sfc. of Instruments. 



The Barometer (the frame of which is brass) is a standard made 

 by Barrow, under the direction of James Glaisher, Esq., of the Green- 

 wich Observatory. 



The adjustment for the difference of capacity of tube and cistern 

 is effected previous to every observation, and the correction for capil- 

 larity and reduction to the temperature of 32° is made at the close 

 of each month. 



The difference between its readings and those of the Greenwich 

 standard is scarcely appreciable, being only 0*002 inch. 



The Dry and Wet Bulb Thermometers, also made by Barrow, are 

 considered to have identical readings under similar circumstances, 

 and both, too, agree with the Greenwich standard thermometer. The 

 Dew-point apparatus, now discontinued, approximates very closely in 

 its readings to the dry and wet bulb thermometers. 



The Self-registering Thermometer is a large Six made by Dollond 

 in 1840, and its average difference from the standard is within j^ths 

 of a degree. A duplicate and precisely similar thermometer (which 

 has also been repeatedly compared with a standard at every part of 

 the scale) is fixed by its side, so that in case of No. 1 getting out 

 of order. No. 2 can be resorted to without detriment to the results. 

 These instruments all have a northern aspect, and are placed 

 about 4 feet above the ground. The naked thermometers employed 

 for indicating the relative amount of solar and terrestrial radiation, 

 are precisely similar to those in use at the Government Observa- 

 tories. 



The Rain and Evaporation Gauges are 8 inches in diameter, and 

 the metres are graduated to the joVo^l^ P^^* ^^ ^^ inch. Both are 

 read off daily. The aperture of the rain-gauge is about 7 feet above 

 the ground. The evaporation dish is mounted on a moveable stand, 

 4 feet 4 inches in height, and the circular shelf on which the vessel 

 rests, is just large enough to hold it. The gauge receives a fair 

 proportion of wind and sunshine, and is always exposed in the open 

 air during the day, except when rain is falling. At night and in 

 wet weather, it is placed under a capacious shed, 9 feet in height, 

 and open in front. Thus, it is conceived that the evaporating sur- 

 face is freely acted upon by all the circumstances concerned in pro- 

 moting this important natural process. 



The direction of the wind is taken twice daily, and its force is 

 registered on an arbitrary scale from to 6 ; the highest number is 

 reserved for storms approaching the hurricane in violence, and is 

 very rarely recorded. 



Remarks on the Weather in 1849. 

 January, — A damp wet month, except the fir.st week, when sharp 



