at Leitk Fort, every Hour of the Day, in 1824 and 1825. 1 9 



which the mean temperature occurred ; for if one of the ob- 

 servations was omitted, the other still possessed considerable 

 value, as an approximation to the mean temperature. Un- 

 fortunately, however, there were almost no observations in 

 existence from which the times of the daily mean temperature 

 could be deduced. Professor Dewey of New York had ob- 

 served the thermometer once every hour, during Jive days at 

 a time, in the months of March, April, July, and October, of 

 the year 1816, and during eight days of January, and two of 

 February, in the year 1817 ; * and Mr Coldstream of Leith 

 registered the temperature of twenty-four successive hours 

 once every month, from July 1822 to July 1823. From this 

 last series of observations, the mean temperature appeared to 

 occur at half-past seven o'clock in the morning, and half-past 

 eight in the evening ; and these hours were accordingly used 

 in most of the registers for 1824 and 1825. It was very ob- 

 vious, however, that these observations, though made with 

 great care, were too limited to afford an accurate result ; and 

 hence it became desirable to record the indications of the ther- 

 mometer for every hour of a complete year. 



As such a plan could only be carried on with effect at a 

 military station, Leith Fort was considered the most eligible. 

 Application was, therefore, made to Colonel Thackeray, com- 

 manding the engineers, and to Colonel Younghusband and 

 Mr Street, of the artillery ; and, as these gentlemen entered 

 warmly into the scheme, preparations were made to begin the 

 register on the 1st of January 1824. A large and accurate 

 thermometer was constructed by Mr Adie for the purpose, 

 and it was placed in a situation as free as possible from all 

 disturbing causes. Its height above the level of the sea is 

 twenty-five feet, and its distance from the sea 200 yards. 



The register commenced on the 1st day of January 1824, and 

 has been regularly and zealously carried on by the non-com- 

 missioned officers of the Fort for two complete years. 



In reducing these observations, Mr Foggo junior of Leith 

 computed all the hourly, monthly, and annual means for the 

 year 1824, and Mr C. Bell made the same calculations for 

 1825. These mean results are given in the following Tables : 



" Mem. American Acad, of Arts and Sciences, vol. iv. Part ii. p. 3f)2 



