56 REPORT — 1851. 



the algebraic sum of one quantity and the conection for temperature, I get 

 the true reading directly, and with little labour ; while there is a great ad- 

 vantage in the cistern being of iron, and in getting rid of the leathern bag 

 which accompanies some barometers of a certain construction. 



On comparing the pressure at Southampton with that at Greenwich 

 monthly, I find a difference varying between 0' 1 1 in. and 0" 1 45 ; the height 

 of Greenwich observatory above my station, measured from the level of the 

 sea, is 100 feet. 



Greenwich. Southampton. DifTerence. 



11 months of 1848 29-711 29-839 0-128 



12 months of 1849 29-801 29-943 0-142 

 12 months of 1850 29-812 29-949 0-137 



The consistent results, arising from reducing the readings to the sea-level and 

 deducting such portion of the pressure as is due to the aqueous vapour in the 

 atmosphere, tend to give considerable confidence in the barometrical obser- 

 vations. 



Mean pressure of dry air reduced to the level of the sea, 



Greenwich. Southampton, Diflference. 



1849 29-692 29-677 -015 



1850 29-697 29-686 -014 



Table II. Determination of the mean temperature The dry and wet- 

 bulb thermometers were compared by Mr. Glaisher and myself with a stand- 

 ard by immersion in water of a high temperature, which was allowed to cool 

 gradually, simultaneous readings being taken from time to time : the result 

 was that the dry-bulb was found to read too high by —-4 in., and the wet- 

 bulb by —-2: to the means of the monthly observations these corrections 

 have been applied ; and by an extended series of simultaneous readings, the 

 indications of the maximum and minimum thermometers have been corrected 

 and reduced to the same standard. 



Mr. Glaisher's corrections for daily range h'dve been applied to the 9 a.m., 

 3 P.M. and 9 p.m. observations, and the mean monthly temperature thus de- 

 duced ; the quantities given by him have also been subtracted from the arith- 

 metical means of the maxima and minima, to obtain an independent mean 

 temperature : although these two results, as may be seen by inspection, are 

 not absolutely identical in every case, they are sufficiently near to show that 

 the variations in the rise and fall of the temperature occur at Southampton 

 at nearly, if not quite, the same local time as at Greenwich. Mr. Glaisher 

 considers that these corrections might not apply to localities on the coast, 

 and that the agreement is nearer than might have been expected. Taking 

 the entire series, the following is the result : — 



1848. 1849. 1850. ^^.°^® 



series. 



M. T. from the daily obs 51-4 50- 2 49*4 50-3 



M. T. from max. and min 52-1 50-1 49-1 50-4 



Difference 07 0-1 03 O'l 



This table also shows the mean of the maxima and minima ; the highest and 

 lowest readings during the month, with the date of their occurrence ; and the 

 differences between these, or monthly range of temperature. 



Table III. gives the monthly means of the readings of the dry and wet- 

 bulb thermometers reduced to the mean temperature by the application of 



