_Methods of Improving the Crop._ The credit of having first systematically formulated the practice of thinnings under the name of _Durchforstung_ (for the first thinning), _Durchplenterung_ (for the later thinnings), belongs to Hartig, although the practice of such thinnings had been known and applied here and there before his time. He confined himself mainly to the removal of the undesirable species, dead and dying, suppressed and damaged trees, being especially emphatic in his advice not to interrupt the crown cover. Excepting the early weeding or improvement cuttings, these thinnings were not to begin until the fiftieth to seventieth year in the broadleaved forest, but in conifers in the twentieth to thirtieth year. The first attempt to explain on a biological basis the process and effect of thinning was made by Späth in a special contribution (1802). Cotta, in his Silviculture, although at first agreeing with Hartig, later in his third edition (1821) changes his mind, and improves both upon the biological explanation of Späth and the practice of Hartig, pointing out that the latter came too late with his assistance, that the struggle between the individuals should be anticipated, and the thinning repeated as soon as the branches begin to die; but he also recognizes the practical difficulty of the application of this cultural measure on account of the expense. Curiously enough, he recommends severer thinnings for fuel-wood production than for timber forests. Pfeil accentuates the necessity of treating different sites and species differently in the practice of thinnings. Hundeshagen accentuates the financial result and the fact that the culmination of the average yield is secured earlier by frequent thinnings. Heyer formulates the “golden rule:” “Early, often, moderate,” but insists that first thinning should not be made until the cost of the operation can be covered by the sale of the material. Propositions to base the philosophy and the results of thinning on experimental grounds rather than on mere opinion were made as early as 1825 to 1828, and again from 1839 to 1846, at various meetings of forestry associations, until, in 1860, Brunswick and Saxony inaugurated the first more extensive experiments in thinnings. The two representatives of forest finance, Koenig and Pressler, pointed out, in 1842 to 1859, the great significance of thinnings in a finance management as one of the most important silvicultural operations for securing the highest yield.