250 Mr Foggo on the Results of' a 



ture 27.7. The mean temperature of January, the coldest month, 

 is 70.8 ; from this the monthly temperature rises till May, of 

 which the temp, is 85 ; after this it declines till the end of July, 

 but, at the approach of the sun in his progress southward, the 

 temperature in October increases to the mean of the year, 

 after which it falls till January. The curve of monthly temp, 

 has, therefore, two convex summits, of unequal elevation, and 

 about 120 days distant from each other. The highest tem- 

 perature observed is 115°, and the lowest 48°; and the ex- 

 treme range of temperature experienced during the two years 

 = 67°. 



The mean temperature of the river is 77.2, agreeing ex- 

 actly with the temperature of the air. At sunrise, the mean 

 temperature is 76.47, and at 3 p.m. 78.03, and the difference 

 between these — 1.56°. 



The highest temperature observed in the river is 88°, and the 

 lowest 68°. The mean height of the river is 2 feet 8 inches, 

 the greatest height being 12 feet, and the lowest 9 inches; 

 but these appear to be relative heights. It is highest in July 

 and August, and lowest in April. The register of the amount 

 of evaporation does not agree with the other observations. The 

 mode of registering was to observe the loss of height in a co- 

 lumn of water of 30 inches, from the 1st of January till the 

 end of the year. We thus observe a gradual diminution of 

 the column of .07 of an inch daily, or 26.5 in the year. As 

 the mean temperature of the air is 77°, an evaporation to this 

 amount would take place though the point of deposition was 

 only 2| below the temperature of the air. But the remark- 

 able range of 27° daily, shows that the climate of this place is 

 one of the driest of the habitable regions of the globe, so that 

 it is probable the evaporameter has been kept within doors, in 

 which case its results would coincide with the indications of 

 thj thermometer in the house, of which the mean is the same 

 as that of the air, and the range is not greater than that of the 

 river. The measure of evaporation must in every case be 

 more or less hypothetical, and Mr Daniell has shown that a very 

 close approximation would be obtained by the difference of elas- 

 tic force of the vapour at the temperature of the air and the dew 

 point. The mean temperature of the air, or of the river, which 



