410 Royal Society. 



taiiiing the moisture or dryness of the atmosphere, a point of cardi- 

 nal importance in all investigations of this nature ; his instrument 

 still continues that which can be best depended upon for this pur- 

 pose. With these accurate instruments, he for three years kept a 

 faithful register of the various atmospheric changes ; he organized 

 the plan adopted by the Horticultural Society in their annual me- 

 teorological reports, a plan which formed the model to the admirable 

 and more extended series of meteorological observations now issued 

 weekly from the Greenwich Observatory under the superintendence 

 of the Astronomer Royal. 



In the year 1824 he communicated to the Horticultural Society 

 an essay 'On Artificial Climate,' which appeared in their Transactions 

 for that year. In this paper among other subjects he insisted on 

 the absolute necessity of attention to the moisture of the atmosphere, 

 as well as of that of maintaining in our hot-houses the moisture as 

 well as the temperature of a tropical climate, if we would produce 

 a vegetation of tropical luxuriance. The publication of this essay 

 caused a complete change in the methods adopted for the culture of 

 plants in general, and particularly of those contained in green- 

 houses and hot-houses, which upon the new plans speedily outgrew 

 the houses provided for their reception. The Society immediately 

 awarded him their silver medal to mark their sense of the import- 

 ance of his views, and now after an experience of more than twenty 

 years, Dr. Lindley, Professor of Botany in University College, not 

 a fortnight before his death, in an article in the Gardener's 

 Chronicle, tracing the origin of the improvements in this branch of 

 horticulture, ascribes the rapid advance in the practice of the art, 

 mainly to the sound and original views promulgated in this essay. 



For the purpose of making more minute and accurate observa- 

 tions upon variations in the atmospheric pressure, Mr. Daniell pro- 

 posed to the Royal Society, in 1830, to construct a barometer in 

 which water should be the fluid used instead of mercury. He was 

 in consequence requested to superintend the construction of such an 

 instrument. Great practical difficulties attended the undertaking, 

 but these he happily surmounted, and the instrument now stands in 

 the Hall of the Apartments of the Royal Society ; he was engaged 

 in re-adjusting it within a few weeks of his decease. On occasion of 

 the late Antarctic Expedition under the command of Captain Sir 

 James Ross, and the establishment by Government of the Magnetic 

 and Meteorological observations, founded a few years since in dif- 

 ferent parts of the British Empire, when the Admiralty applied to the 

 Royal Society for instructions as to the nature and extent of the ob- 

 servations to be made, Mr. Daniell was requested by the Committee 

 of Physics of the Royal Society, to draw up the Meteorological por- 

 tion of these directions. The paper which he then prepared fur- 

 nished the basis of that part of the Report of the Committee, pub- 

 lished in the year 1840, under the sanction of the Royal Society. 



But it was not alone to meteorology, and its practical applications, 

 that his labours were confined ; his researches upon various chemical 

 subjects were not less numerous or important. More than forty 



