254 Mr Foggo on the Results of a 



sure at 4 a. m. is 0.027 below that of 10 a. m., and .047 above 

 4 p. m. The average of 10 a. m. is .074 above 4 p. m. In 

 the last three months the average of 8 p. m. is .006 below that 

 of 4 a. m., .04 above 4 p. m., and .041 below 10 a. m. I do 

 not find one instance of the horary oscillations being suspend- 

 ed ; but during the prevalence of the S. W. monsoon the ex- 

 tent of the variation is diminished. See Table II. col. 9, 10, 11. 

 Besides the horary oscillations, there is a monthly variation 

 from the annual mean pressure of remarkable regularity, when 

 it is considered that the results are obtained from one year's 

 observations only. This variation, however, is not the same 

 at each hour of observation, so that the decrement has reach- 

 ed its maximum for 4 a. m. and 4 p. m. in June, but for 10 

 a. m. not till July. It appears to be occasioned by the united 

 effects of increase of vapour and the influence of the monsoons. 



The amount of this variation is .262. The maximum pres- 

 sure observed throughout the year is 27.79, and the minimum 

 27.34 ; extreme range 4.5. 



The mean height of the river this year was 3 feet. The 

 amount of rain measured 23.7 inches, and the probable amount 

 of evaporation 122 inches. I have calculated a hygrometric 

 table for this year (Tab. III.) according to the method men- 

 tioned above, which is perhaps as near the truth as any simi- 

 lar table for an intertropical climate that has been published. 



Monthly Results for 1816. 



In January, the temperature is at its minimum, but the pres- 

 sure has attained its maximum, the N. E. monsoon is fairly esta- 

 blished, and the weather clear, without rain or thunder. The 

 mornings generally hazy, from the rapid evaporation occasion- 

 ed by the energy of the sun's rays. Copious dews fall during 

 the night, and particularly before sunrise. The only two 

 mornings on which no dew was observed were subsequent to the 

 two coldest days of the year, the 7th and 15th ; lightning was 

 seen only once, on the evening of the 16th. The height of the 

 river on the first of the month, 2 feet 3 inches. 



February. — Weather in general the same as last month ; 

 lightning more frequent at night ; and rain apparently all 

 round the horizon on the hills. On some mornings the wind 



