average January temperature is below the freezing point. This same condition marks most of the great wheat regions of the world.

The wheat countries (which are also the countries of oats, barley, and rye) are where the summer season only is the growing season, and the comforts of winter must be provided for by forethought and labor; and hence they are also the countries of labor, industry, and enterprise, and where the highest civilization has been developed, the result being correlated to these climatic conditions.

The table of distribution according to rainfall (Table XXII, p. 16) shows that 132,152,234 bushels, or 28.8 per cent of the crop, grows with an annual rainfall of between 40 and 45 inches, 62.7 per cent where it is between 35 and 50 inches, and 92.4 per cent where the annual rainfall is above 25 inches, although some important wheat regions, notably those of California, are where the mean annual rainfall is less than 25 inches. We have an explanation of this in the seasons at which the rain falls. The table of distribution according to the rainfall of the growing season (Table XXIII, p. 16) shows that 220,656,637 bushels, or 48 per cent of the crop, grows where from 20 to 25 inches of rain falls during this season, and 366,381,658 bushels, or 79.7 per cent, where the rainfall during the growing season is from 15 to 25 inches, 6.4 per cent where it is below 15 inches, and only 1 per cent where it is less than 10 inches-a fact of much significance for great tracts of our country.

CULTIVATION OF CEREALS—EXPERIMENTS AT BROOKINGS, S. DAK.

WHEAT.

The first annual report of this station, for the year ending June 30, 1888, gives following table of results of experiments on different varieties of wheat, at Brookings, S. Dak. (lat. 44.3° N.; long. 98.5° W.), in April and May, 1887, on plats of ground that had already borne one crop of wheat or flax or oats. Some were sown broadcast and had no subsequent cultivation; others were "drilled by hand and subsequently hoed twice or thrice.

The columns giving the calculated sums of degrees of temperat are based upon observations at the Signal Service station at F some distance to the westward, because the special station at ings was not then established. The meteorological table f follows the agricultural tables, so that the student may further studies as he desires. A fragment of the record at Brookings for 1888 is given in the statior which I have compared with the record for Hurc important error will result from using the Huro

TABLE III.-Barbados sugar crop and rainfall of preceding year.

NOTE. In calculating the average crop and the respective annual excesses or deficits given in Tables I and III Governor Rawson says that "he has made an arbitrary division of the whole period into two sections marked by the introduction of the use of guano as a fertilizer." For the first section, 1847-1856, inclusive, he considers 38,795 hogsheads as the average, but for the second section, 1857-1872, inclusive, he takes 45,036 hogsheads as the average. He states that this is virtually assuming that during the whole period climatic and other conditions were nearly constant and that the principal difference was in the introduction of the use of guano and the great increase of crops was due to that. During the first interval an inch of rain corresponded to 642 hogsheads of sugar in the crop of the next year, but during the second interval it corresponded to 800 hogsheads.

PART III.-STATISTICAL FARM WORK.

Chapter XIII.

THE CROPS AND CLIMATES OF THE UNITED STATES.

The ultimate object of our inquiry is to determine the exact percentage of the effect of normal and abnormal climates upon special crops in special regions of this country and the relation to the whole crop of the United States. To this end we must first ascertain the climatic effect on the yield per acre, and this is our present special problem, leaving it to the statistician and census taker to ascertain how many acres are under cultivation and what the actual effect will be in bushels or pounds. The climatologist, or Weather Bureau, has only to determine numerically the climatic effect upon a given unit area.

The tables of yield per acre for ten important crops and for all years will be given in a subsequent portion of this section, but the study of these must be preceded by several studies into matters that are not strictly climatic, but which nevertheless enter into the statistics of actual harvests and obscure the strictly climatic influences. Thus the statistics must be corrected in some way for the effect of the customary modes of cultivation and the quantity of seed that is sown, on which point I give statistics appropriate to the United States.

Again, before comparing our climatic data with the phenomena of vegetation we must know something of the average date of seeding, with respect to which I have given the dates for seeding of winter wheat.

The corresponding dates for rye will not differ very much. The dates for maize, potatoes, tobacco, and cotton have already been given for special localities, but still require to be tabulated in a general way. The necessary climatic data are given in my next section for twenty Signal Service stations, and I regret that the shortness of time has not allowed me to give more complete data for these and for all other stations, but the tables here presented will serve to show the form in which such data should be presented for the greatest convenience in phenological studies.

But before entering upon so extensive a system of numerical comparisons it is necessary to bear in mind certain principles which I would illustrate in the following remarks.

VARIABILITY OF RESULTS FROM PLAT EXPERIMENTS.

The reliability of the data obtained from experiments on small plats of ground, and on which we should naturally place much reliance in discussing the relation between climates and crops, is a matter of the first importance, and we must begin our study with an attempt to obtain a clear idea as to the extent to which such data are fit to be used as a basis for our studies. In the light of all that has thus far been ascertained with reference to the nature of the influences at work to increase or diminish the resulting crop, we may safely say that the results obtained from two different plats will not be comparable with each other and still less be applicable to the larger fields harvested by the farmers, unless we know for each plat or field the absolute or relative conditions as to the following matters:

(1) The mechanical condition of the soil as affecting aeration, percolation, and temperature.

(2) The chemical nature of the original soil.

(3) The character, proportion, and uniformity of distribution of the fertilizers and the history of the previous rotations of crops on these plats; the influence of climate, rain, and drainage on the available nutrition in the soil.

(4) The dates of cultivation and application of the fertilizers. (5) The exact area of the plats.

(6) The distance apart of the hills or stalks.

(7) The number and quality of seeds sown per acre.

(8) The moisture in the soil at the beginning and the quantity and times of rain or irrigation.

(9) The chemical and biological quality of the rain or irrigation water-i. e., rain or snow water; rain with much or little nitrogenous compounds and biological germs.

(10) The injury by insects and animals.

(11) The temperature of the soil.

(12) The remaining climatic details as to heat, sunshine, dryness, and velocity of the wind.

(13) The sterility of the soil as to the microbic life that seems indispensable to the success of certain crops or to the growth of the plants.

(14) The nature of the climate in which the seed and its immediate ancestor was grown.

In the total absence of knowledge as to many of these points and fragmentary knowledge on others, a simple direct comparison between the results of two plats lying side by side and that have in some few respects been treated alike must be entirely misleading. But the extent to which such comparisons are deceptive, or rather the