1 88 The Soli in Relation to Disease. [part i. 



analyses. As it is unnecessary to reproduce all these figures, we have confined our- 

 selves to giving tables of the amount of carbonic acid per 1,000 volumes of soil-air at 

 0** C. and at 760 m.m, barometric pressure. Our acknowledgments are due to 

 Mr. C. H. Wood, the Officiating Professor of Chemistry at the Medical College, for 

 valuable aid in indicating the simplest and most accurate method of recording 

 the data required in connection with this matter. 



(6) — Soil-temperature. 



The data recorded on this point are also the result of our own observations 

 and were obtained in the following manner : — A shallow shaft or well was sunk 

 to a depth of slightly over 6 feet in the ordinary alluvium of Calcutta. The 

 shaft having been made of sufficient capacity to allow of easy entrance, was lined 

 with bricks and mortar. An opening was left in the floor to allow of easy drainage 

 of any surface water which might obtain entrance, and two openings were left in 

 the brickwork of one side of the shaft at depths of 3 and 6 feet, respectively, 

 leading into wide tubes of perforated zinc, which penetrated the soil horizontally 

 from the outer surface of the brickwork and terminated in open extremities in 

 the earth. 



These tubes were of sufficient diameter to allow of a narrow board, carrying 

 the thermometers, being pushed into them. The thermometer board had a wooden 

 plug and handle which fitted into the mouth of the tube whilst the opening in 

 the brickwork was closed by an accurately adjusted wooden cover, and further 

 secured by being coated externally with moist clay. 



A thick wooden lid, covered by a layer of turf, closed the mouth of the 

 shaft, and the entrance of rain or access of sun to the cover was prevented by 

 means of a thatch roof about 5 feet above the ground. 



Observations were made daily at 11 a.m., and the thermometers immediately 

 returned to their places in the perforated zinc tubes let into the earth, care 

 being taken to raise the temperature of the minimum and to depress that 

 of the maximum, respectively, considerably above and below the temperature of the 

 soil. 



(c) — Open-air temperature; (d) — Rain-fall; and {e)— Wind-velocity. 



The figures in Tables I — VI, upon which the charts are based, of daily and 

 average weekly atmospheric temperature ; of rain-fall ; and of the velocity of the 

 wind were obtained from the " Abstract of the Results of the Hourly Meteorological 

 Observations taken at the Surveyor Greneral's Office, Calcutta " as published in 

 the Proceedings of the Asiatic Society of Bengal ; but the monthly statements 

 in Table VII of the atmospheric temperature and rain-fall are from the Annual 

 Reports of the Meteorological Reporter to the Government of Bengal. 



