As the extractions are made by heats far superior to any natural ones, though the actual temperature of the air neither adds to, nor diminishes from, their strength, yet it is to be known for the following reason. The proper heat given to the mash is by means of cold added to boiling water; and cold water generally is of no other heat than that of the air itself. Indeed, when the cold is so intense, as to occasion a frost, and to change water into ice, that which is then used for brewing, being mostly drawn from deep wells, or places where frost never, or but seldom, takes place, may be estimated at 35 degrees, and this will be sufficiently exact. The following table shews the temperature of the air for every season in the year, and confirms what I have just now said concerning the season proper for brewing, and the actual heat of the water. It was deduced from many years’ observations, made with very accurate instruments, at eight o’clock in the morning, the time in which the heat is supposed to be the medium of that of the whole day. A table, _shewing the medium heat, for every Season of the year, in and about London, deduced from observations made from 1753 to 1765, at eight o’clock each morning_. Degrees. January 1 } 36′ 38 July 1 } 60′ 52 to 15 } to 15 } to 31 } 34′ 97 to 31 } 60′ 29 February 1 } 35′ 51 August 1 } 59′ 89 to 14 } to 15 } to 28 } 38′ 11 to 31 } 58′ 48 March 1 } 37′ 99 Septemb. 1 } 55′ 17 to 15 } to 15 } to 31 } 39′ 72 to 30 } 54′ 13 April 1 } 43′ 13 October 1 } 48′ 66 to 15 } to 15 } to 30 } 46′ 04 to 31 } 46′ 72 May 1 } 49′ 05 Novemb. 1 } 42′ 26 to 15 } to 15 } to 31 } 53′ 67 to 30 } 39′ 40 June 1 } 57′ 20 Decemb. 1 } 38′ 61 to 15 } to 15 } to 30 } 59′ 14 to 31 } 37′ 54 To ascertain the authority of this table, and to make it useful to several purposes, I have carried to decimals the mean numbers resulting from my observations.—But such an exactness has been found, in the practice of brewing, to be more troublesome than necessary. I have therefore constructed another table, similar to the former, but where the fractions are omitted, and the whole numbers carried on from five to five. The heats of the latter end of October, and beginning of November, have here been set down rather higher than they really are; as, at this time of the year, the hops fit to brew with are old and weak, and I could not devise any means more easy to allow for their want of strength. A TABLE, _shewing the medium heat of the air, in and about London, for every season of the year, applicable to practice_. Degrees. Degrees.