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276 Sir G. B. Airy. On the [Nov. 23, 



I. " Monthly Means of the Highest and Lowest Diurnal Tem- 

 peratures of the Water of the Thames, and Comparison 

 with the corresponding Temperatures of the Air at the 

 Royal Observatory, Greenwich." By Sir George Biddell 

 Airy, K.C.B., F.R.S., late Astronomer Royal. Received 

 September 15, 1882. 



In presenting to the Royal Society a partial reduction of the 

 thermometrical observations made in the water of the Thames during 

 a period of thirty-five years, I commence with a brief history of the 

 undertaking and progress of this work. 



The observations were instituted at the suggestion of the con- 

 ductors of the Medical Department in the Office of the Registrar- 

 General of Births, Deaths, and Marriages, with the view of supplying 

 some knowledge of an element which may possibly affect the sanitary 

 condition of the Metropolis. The plan of observations was arranged 

 at the Royal Observatory of Greenwich; and the instruments were 

 procured and mounted, and repaired, when necessary, under the care 

 successively of James Glaisher, Esq., and William Ellis, Esq., 

 Superintendents of the Magnetical and Meteorological Department of 

 the Observatory. The self-recording instruments were attached to 

 the Hospital Ships successively anchored in the Thames, nearly 

 opposite to Greenwich : and their records were read and registered by 

 the medical officers of those ships, and these written registers were 

 transmitted every week to the Royal Observatory. And I cannot too 

 strongly express my sense "of the care with which the observations 

 were made, the fidelity with which they were recorded, and the order 

 and regularity with which they were transmitted to the Royal 

 Observatory. The weekly register, when received at the Observatory, 

 was combined with the brief record of other meteorological facts 

 observed at the Royal Observatory, and (with the medical record) 

 was published every week by the Registrar- General. 



I have been favoured by Mr. Ellis, who, at my request, has kindly 

 superintended the preparation of the results of observations of 

 thermometers in the water of the Thames, with the following remarks 

 on the nature of the observations and the elements for their reduction. 



"The observations, from the commencement of the series in May, 

 1844, until April, 1870, were taken at the 'Dreadnought' Hospital 

 Ship, moored in the river a little above Greenwich. The thermo- 

 meters were inclosed in an upright wooden trunk attached to the side 

 of the ship, its lower portion projecting into the water ; the trunk 

 was closed at the bottom ; the closing plate and that portion of the 

 sides which was under water being perforated with holes, to allow the 

 water easily to flow through. The thermometers were suspended in 



