On looking over the table it will be seen that there are three principal periods when the eccentricity rose to a very high value, with a few subordinate maxima between. It will be perceived also that during each of those periods the eccentricity does not remain at the same uniform value, but rises and falls, in one case twice, and in the other two cases three times. About 2,650,000 years back we have the eccentricity almost at its inferior limit. It then begins to increase, and fifty thousand years afterwards, namely at 2,600,000 years ago, it reaches ·0660; fifty thousand years after this period it has diminished to ·0167, which is about its present value. It then begins to increase, and in another fifty thousand years, namely at 2,500,000 years ago, it approaches to almost the superior limit, its value being then ·0721. It then begins to diminish, and at 2,450,000 years ago it has diminished to ·0252. These two maxima, separated by a minimum and extending over a period of 200,000 years, constitute the first great period of high eccentricity. We then pass onwards for upwards of a million and a half years, and we come to the second great period. It consists of three maxima separated by two minima. The first maximum occurred at 950,000 years ago, the second or middle one at 850,000 years ago, and the third and last at 750,000 years ago—the whole extending over a period of nearly 300,000 years. Passing onwards for another million and half years, or to about 800,000 years in the future, we come to the third great period. It also consists of three maxima one hundred thousand years apart. Those occur at the periods 800,000, 900,000, and 1,000,000 years to come, respectively, separated also by two minima. Those three great periods, two of them in the past and one of them in the future, included in the Table, are therefore separated from each other by an interval of upwards of 1,700,000 years. [Illustration: PLATE IV W. & A. K. Johnston, Edinb^r. and London. DIAGRAM REPRESENTING THE VARIATIONS IN THE ECCENTRICITY OF THE EARTH’S ORBIT FOR THREE MILLION OF YEARS BEFORE 1800 A.D. ONE MILLION OF YEARS AFTER IT. _The Ordinates are joined by straight lines where the values, at intervals of 10,000 years, between them have not been determined._] In this Table there are seven periods when the earth’s orbit becomes nearly circular, four in the past and three in the future. The Table shows also four or five subordinate periods of high eccentricity, the principal one occurring 200,000 years ago. The variations of eccentricity during the four millions of years, are represented to the eye diagrammatically in Plate IV. In order to determine with more accuracy the condition of the earth’s orbit during the three periods of great eccentricity included in Table I., I computed the values for periods of ten thousand years apart, and the results are embodied in Tables II., III., and IV.