V. AGRICULTURAL. 541 



supply weighed quantities of water as needed, but which was, at other times, 

 closed by a cork. To prevent, as far as possible, evaporation from the soil 

 other than through the plant itself, small pieces of glass were laid over the 

 centre hole, close up to the stems of the plants as they grew. Each jar held 

 about 42 Ibs. of soil. A standard leaden counterpoise was kept in the weight 

 pan, and only the deviations above or below its weight were determined ; a set 

 of weights, from 10,000 grains down to one-tenth of a grain, being provided 

 for the purpose. The weighings were generally taken at intervals of 10 days, 

 but sometimes at shorter periods. 



The list of plants experimented upon included wheat, barley, beans, peas, 

 clover, mangold wurzel, turnips, and various evergreen and deciduous trees. 



2742. Case of Casts of White Silesian Sugar-beet, illus- 

 trating the influence of different manures on the amount of produce, 

 and on the per-centages of dry matter and of sugar in the roots. 

 First season of the experiments, 1871. John Sennet Lawes. 



2743. Also Table of Average Results obtained on growing 

 the crop five years in succession on the same land. 



John Bennet Lawes. 



Experiments conducted on the farm of John Bennet Lawes, Esq., 

 Rothamsted, near St. Albans. 



2744. Apparatus used in an investigation by Messrs. Lawes, 

 Gilbert, and Pugh, to, determine whether plants assimilate free or 

 uncombined nitrogen ; with drawings of some of the plants grown. 

 See Philosophical Transactions, Part 2, p. 493, 1859; and 

 Journal of the Chemical Society, new series, vol. i. ; Entire 

 Series, vol. xvi., 1863. John Bennet Laives. 



The tap being opened, and water allowed to flow from a raised reservoir 

 into the large stoneware Woulfe's bottle, air passes from it by the small 

 leaden exit tube, through two glass Woulfe's bottles containing sulphuric 

 acid, then through the long tube filled with fragments of pumice saturated 

 with sulphuric acid, and, lastly, through a Woulfe's bottle containing a 

 saturated solution of ignited carbonate of soda ; and, after being so washed, 

 it enters the glass shade, from which it passes by an exit tube through an 

 eight-bulbed apparatus containing sulphuric acid, by which communication 

 with the unwashed external air is prevented. Entering with the shade at 

 the side opposite to this exit tube is a tube for the supply of water or solutions 

 to the soil, but which is at other times closed. In front of the shade is a 

 bottle connected by a tube with the bottom of the earthenware lute-vessel, for 

 the collection of the condensed Avater, which is from time to time withdrawn 

 from the bottle by suction, and returned to the soil. The shade enclosing 

 the pot and plant stands in the groove of a specially made, hard-baked, 

 glazed, stoneware lute-vessel^ mercury being the luting material. Carbonic 

 acid is supplied as occasion may require, by adding a measured quantity of 

 chlorhydric acid to the bottle containing fragments of marble, the evolved 

 gas being, as will be seen, washed through one of the bottles of sulphuric 

 acid, through the long tube, and through the carbonate of soda solution, 

 before entering the shade. The short leaden pipe, bent and opening down- 

 wards externally to the large stoneware bottle, passes nearly to the bottom 

 of it inside, and is a safety tube for the overflow of the water when the vessel 

 is full, and so to prevent it passing into the wash bottles, &c. When full, 

 the cork near the bottom of the stoneware vessel is withdrawn, and the water 

 flows by means of a drain back into a tank, from which it is pumped into 



