AND METEOROLOGY OF DUKHUN. 1^ 



turnal atmospheric tides ; but it answered sufficiently well as a check upon my other 

 barometers. Several others by Gilbert, used by myself and my friends, were found 

 to be similarly defective. 



Auxiliary to the barometers, I had in use Adie's sympiesometer. This instrument, 

 so ingenious in its construction, I soon found to be utterly inadequate to measure 

 the pressure of the atmosphere with the correction given to it for the expansion from 

 heat of the hydrogen gas in the tube. An inspection of my meteorological register 

 will show by a glance the inefficiency of the instrument as a substitute for the baro- 

 meter within the range of my observations. In fact, it constantly sunk with increase 

 of heat, and gradually rose with the return of cold. In very few instances in a whole 

 year was it found to have stood higher at 9| a.m., the period of the maximum atmo- 

 spheric pressure, than at sunrise ; and in these trifling approximations to truth it 

 evidently deteriorated since the first record of its indications. A sympiesometer 

 in possession of the Assay Master at Bombay was subject to the same defects. I 

 nevertheless continued my observations with the instrument simultaneously with the 

 barometers, to supply the inventor with the necessary elements for its correction, 

 should he desire to make use of them. I was further induced to keep the instru- 

 ment on my register, from the advantages I derived from the attached elegant and 

 accurate thermometer, which had its degrees divided into fifths. 



The temperature of the air was determined by two excellent Dollond's Fahren- 

 heit thermometers, one of which had been in my possession twenty-two years. One 

 had a brass scale, the other a stout ivory scale sufficiently robust to prevent the 

 dry air warping it materially. These thermometers never differed from each other 

 more than half a degree, and I had great confidence in their indications. No. 1. with 

 the brass scale was used for several years to determine the temperature of boiling 

 water at different levels. In this process small particles of mercury rose from the 

 surface, and fixed themselves at the apex of the tube ; but this was easily remedied 

 by driving the mercury by heat up to the apex, and in retiring it always carried with 

 it the particles which had risen. 



For the determination of the moisture in the atmosphere, two of Leslie's and one 

 of Daniell's hygrometers were sent to me from Calcutta. The former were kept in 

 use from the 21st of March 1826 until the 7th of April 1827, when, finding them 

 destitute of uniform indications with respect to each other and to Daniell's hygro- 

 meter, I was induced to give up employing them further. Daniell's hygrometer 

 was continued in use from the 21st of March 1826 until the 30th of September 1827, 

 when it was unfortunately broken. There not being an instrument of the kind for 

 sale in India, Colonel Goodfellow, Chief Engineer at Bombay, was good enough to 

 assist we with one, which was brought into use on the 25th of October following. 

 This continued in use, with occasional interruptions from the want of aether, until 

 the 28th of March 1828, when it shared the fate of the former. From this period 

 until the Uth of June 1829, I was disabled from making hygrometric observa- 



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