Weighed portions of each are partially dried, and preserved for future reference or analysis. Duplicate weighed portions of each are dried at 100° C, the dry matter determined, then burned to ash on platinum sheets in cast-iron muffles. The quantities of ash are determined and recorded, and the ashes themselves are preserved for reference or analysis. In a large proportion of the samples the nitrogen is determined, and in some the amount existing as albuminoids, amides, and nitric acid.
"In selected cases—illustrating the influence of season, manures, exhaustion, etc. complete ash-analyses have been made, numbering in all more than seven hundred. Also in selected cases, illustrating the influence of season and manuring, quantities of the experimentally grown wheat-grain have been sent to the mill, and the proportion and composition of the different mill-products determined.
"In the sugar-beet, mangold-wurzel, and potatoes, the sugar in the juice has in most cases been determined by the polariscope, and frequently by copper also.
"In the case of the experiments on the mixed herbage of permanent grass-land, besides the samples taken for the determination of the chemical composition (dry matter, ash, nitrogen, woody fiber, fatty matter, and composition of ash), carefully averaged samples have frequently been taken for the determination of the botanical composition. In this way, on four occasions, at intervals of five years—viz., in 1862, 1867, 1872, and 1877—a sample of the produce of each plot was taken and submitted to careful botanical separation, and the percentage, by weight, of each species in the mixed herbage determined. Partial separations, in the case of samples from selected plots (frequently of both first and second crops), have also been made in other years."
This condensed statement of the plan of the field experiments, and brief outline of some of the work performed in connection with them, from the "Memoranda" for June, 1882, will give some general idea of the extent of the Rothamsted Station, and of the thorough manner in which all operations are conducted; but, in our enumeration of the other lines of inquiry now in progress, we can only mention the subjects of investigation without referring to particulars in the methods practiced, as we wish to save space for a discussion of some of the leading results that have been thus far obtained.
More than one thousand samples of soil have been taken from the experiment-plots, at different depths, for the purpose of analysis, to ascertain the rate of soil-exhaustion under different conditions, and to trace the relations of the soil to the crops grown and to the manures applied.
For nearly thirty years the rain-fall has been measured in a gauge having an area of one thousandth of an acre, and frequent analyses have been made to determine the available supply of combined nitrogen in the form of ammonia and nitric acid that can be obtained by