18S5.] 



Meteorological Observations at Nasirabdd. 



51 



Mean Results of four Years' Observations. 



1 



Barometer Temperature . 



Mean 









Months. 



at 32 







of Air 





Temperature. 



S. 



T. 



G. 





4 P. M. 



var. 



4 P. M. 



var. 



Day. 



6 



Night. 





inches. 















u 





January, 



28.475 



+ .232 



70.6 



—17.0 



60.9 



57.5 



31.6 



.550 



2.36 



February, 



.387 



+.151 



72.2 



—11.4 



66.4 



59.0 



34.9 



.368 



2.66 



March, . . 



.316 



+.080 



84.0 



— 4.4 



73.5 



70.5 



34.9 



.265 



2.66 



April 



.224 



010 



95.5 



+ 5.6 



83.6 



81.5 



37.4 



.194 



2.80 



May, 



.109 



127 



101.8 



+ 14.7 



92.6 



88.2 



40.1 



.175 



3.06 



June, .... 



27.997 



—.239 



100.7 



+ 14.6 



92.5 



87-7 



63.3 



.388 



6.52 



July, 



.974 



—.262 



92.8 



+ 9.6 



87.5 



83-8 



71.7 



.604 



8.60 



August, . . 



28.024 



—.212 



88.8 



+ 5.7 



83.6 



81-1 



71.5 



.679 



8.60 



September, 



.137 



— 099 



90.9 



+ 6.1 



84.0 



80.9 



66.4 



.578 



7.39 



October,. . 



.305 



+ .069 



90.2 



+ 2.3 



80.7 



76.8 



46.7 



.334 



4.00 



November, 



.431 



+ .195 



79.3 



— 7.7 



70.2 



66.7 



43.2 



.392 



3.47 



December, 



.451 



+ .215 



67.3 



—18.3 



59.6 

 77-9 



56.7 



38.2 



.479 



3.05 



Means, . . 



28.236 



1 .478 



86.2 



1 33.0 



74.2 



48.3 



.417 1 4.60 



The mean temperature (day and night) from these four year's observations is 

 76°; but as Nasirabad is elevated above the level of the sea nearly 1500 feet, 

 the air is or ought to be cooler on that account by about 5 B, 5, so that the tem- 

 perature at the sea level would be 81 - 5, which is that assigned to the equator by 

 Humboldt. 



If we calculate the mean temperature for the latitude (26" 18') by the formulae 

 which have been found in most cases to agree well with observation, we shall 

 have, q 



By Mayer's, T (= 84°— 52° sin 2 L) , = 73-8 



Brewster's, T (= 81°-5 cos. L) = 73-1 



Daubuisson's,.. T (= 27 d cos. 2 L in centesimal degrees*) .... = 71 - 



Atkinson's T (= 97 0, 08 cos-| L— 10 6 -53) = 71.9 



Mean = 72.5 



which is 9° less than the observations give when reduced to the sea level. But 

 it must be observed with regard to the locality of Nasirabad that it stands on 

 an arid rock on which scarcely any vegetation exists unless during the rainy 

 season : this will no doubt account for a part of the difference. Mr. Atkinson 

 in his elaborate paper on Astronomical and other Refractions, (vide Memoirs of 

 the Royal Astronomical Society, 2nd volume,) considers that 4° may be deducted 

 from the observed temperatures of "large extended plains:" allowing this, we 

 have still 5° unaccounted for. However, on calculating by the same formulae, 

 the mean temperatures of several places in this country where observations have 

 been made and recorded in this Journal, I find similar differences, part of which 

 may very probably be owing to errors in the instruments used, as it is well known 

 how great a difference exists in the thermometers manufactured for exportation 

 to this country, no two of which are hardly ever found to agree in their indica- 

 tions, some differing several degrees from others. In the subjoined table, the 

 latitudes and elevations of some of the places are given by rough estimation, not 

 having at hand the means of ascertaining them accurately, but any probable 

 errors in these estimations cannot affect the results materially. The difference of 

 temperature due to elevation has been calculated by Mr. Atkinson's Formula,, 

 viz. 



Required diff. in degrees 



251 + 



- h being the elevation in feet. 



200 



* Or, in Fahrenheit's Scale. 

 H 2 



T=80 o, 6— 48 0, 6 sin '■ ' L. 



