[56] Even larger estimates of the number of germs in a gramme of soil have been made--from three-quarters to one million (Koch, Fuelles, and others). [57] These organisms consist of molds, yeast, and bacteria, the last-named being most abundant. In the surface-soil, among the bacteria, bacilli are most abundant. Micrococei are not abundant. [58] Investigated by Winogradsky, Olivier, De Rey Pailhade, and others. [59] Organisms of this kind have been investigated among others by Heraues, Hueppe, and E. Wollny. According to the two first-mentioned investigators, certain colourless bacteria effect the formation in the absence of light from humus and carbonates a body resembling in its nature cellulose. [60] Investigated by Springer, Gayon and Dupetit, Deherain, and Marguenne. APPENDIX TO CHAPTER I. NOTE I. (p. 68). The following determinations by Schuebler show the absorptive power of different kinds of soil-substances. These were obtained by soaking weighed quantities of the soil in water, and allowing the excess of liquid to drain away, and weighing the wet earth. Per cent of water absorbed by 100 parts of earth. Siliceous sand 25 Gypsum 27 Calcareous sand 29 Sandy clay 40 Strong clay 50 Arable soil 52 Fine calcareous 85 Garden-earth 89 Humus 190 It has been calculated that the absorptive power of a mixture of different substances is not simply equal to the sum of their separate ingredients. NOTE II. (p. 74). EVAPORATION. The retentive property of a soil for water tends to retard evaporation. The following table by Schuebler shows the rate at which evaporation proceeds in different soils. The experiment was conducted in the following way. The soil experimented upon was saturated with water and spread over a disc, and allowed to evaporate for four hours, when it was weighed. The amount of time required for the evaporation of 90 per cent of the water was also estimated. Of 100 parts of water in the wet soil there evaporated, at 60 deg. Fahr.-- Time required to In four hours-- evaporate 90 per cent. From-- per cent. Hours. Minutes.