[2] Van Helmont's science was, however, of an extremely rudimentary nature, as may be evidenced by the belief he entertained that the smells which arise from the bottom of morasses produce frogs, slugs, leeches, and other things; as well as by the following recipe which he gave for the production of a pot of mice: "Press a dirty shirt into the orifice of a vessel containing a little corn, after about twenty-one days the ferment proceeding from the dirty shirt, modified by the odour of the corn, effects a transmutation of the wheat into mice." The crowning point in this recipe, however, lay in the fact that he asserted that he had himself witnessed the fact, and, as an interesting and corroborative detail, he added that the mice were born full-grown. See 'Louis Pasteur: His Life and Labours.' By his Son-in-law. Translated by Lady Claud Hamilton. (Longmans, Green, & Co.) P. 89. [3] He then goes on to relate a number of experiments by Cornelius Drebel and Albertus Magnus, showing the refreshing power of this balsam, and then those of Quercitan with roses and other flowers, and his own with nettles. [4] Priestley, however, did not realise that _carbonic acid gas_ was a necessary plant-food; on the contrary, he considered it to have a deleterious action on plant-growth. Percival was really the first to point out that carbonic acid gas was a plant-food. [5] It is recorded as an instance of the scientific enthusiasm of the man, that he was wont to carry about with him bottles containing oxygen, which he had obtained from cabbage-leaves, as also coils of iron wire, with which he could illustrate the brilliant combustion which ensued on burning the latter in oxygen gas. [6] For a full account of Senebier's researches, see 'Physiologie vegetale, contenant une description des organes des plantes, et une exposition des phenomenes produits par leur organisation, par Jean Senebier.' (5 tomes. Geneve, 1800.) [7] How Crops Grow. By Professor S. W. Johnson. Macmillan & Co. (Introduction, p. 4.) [8] See p. 40 to 45. [9] Elements of Agricultural Chemistry, in a course of Lectures for the Board of Agriculture. By Sir Humphry Davy. (London, 1831.) [10] This department of agricultural research was subsequently carried on by Sprengel, Schuebler, and others. [11] Born in Paris, 1802; died 11th May 1887. [12] See p. 40. [13] While much of Boussingault's work was carried out previous to the year 1840, he continued to enrich agricultural chemistry with numerous valuable contributions up till the time of his death. It may be well here to mention the names of his most important contributions to agricultural science, made subsequent to 1840. In 1843 he published, in a work entitled 'Economie Rurale,' the results of his numerous experiments and researches. This work is well known to English agriculturists from an English translation which appeared in 1845 (Boussingault's 'Rural Economy,' translated by G. Law. H. Balliere, London).