thoughts recurred to this man, and I made him the hero of a little sketch in rhyme,as will be found in the next chapter, under the title of, "A Retrospection."

PERPETUAL MOTION.

When in my fourteenth year, an older schoolmate explained to me, in a general way, the subject of "Perpetual Motion," of which he had been reading. I became interested at once, and later gave the matter a good deal of thought; the result being, that when I was sixteen, I turned my hand for the first time to invention, by undertaking to produce a perpetual motion machine, after a plan which I conceived and reduced to drawing, which was plausible enough to arouse the interest and enthusiasm of those who were priveleged to examine it.

But I early learned what all must sooner or later learn, who take up this fascinating study-that action and reaction are always equal, and in opposite directions; and that gravity acts just as forcibly on an ascending

body, as on a descending one; while no body can exert a greater force in descending from a given point, than is required to raise it to that point again, no matter by what route it travels.

A little later my mind was incidentally turned to the subject which afterward became my life study. It was my privelege to observe an important, though not quite total eclipse of the sun; and as I saw that well defined, circular shadow sweep over the sun's disc, I fell to meditating on the cause of the strange phenomenon. I had learned nothing of astronomy up to that time, but that dark, curved or circular,— something, passing between me and the sun, impressed me as being some other heavenly body which, I correctly theorized, night be the moon.

Soon feeling confident that I had discovered the cause of this phenomenon, I began to extend my inquiries, and having a fair general knowledge of geography- the location and significance of the equator and the

tropics, lines of latitude and longitude, with reference to the location of my home, &c, I conceived the bold project of attempting what I learned in after years, is the most important problem in astronomical science --that of calculating the distance of the sun from earth; technically called "Finding the solar parallax."

I had learned that at the time of the equinoxes-on the 21st. day of March, and on the 23d. day of September, the sun is directly over the equator, and on consulting the map, I found that my home, (from which my observations would be made,) was nearly on the 43d. parallel of north latitude. I reasoned that whatever angle the sun's rays made, at high noon on those days, with a line perpendicular to my point of observation, if that angular line were continued till it cut a line drawn upward, perpendicular to the earth at the equator, the point of intersection of the two lines, would represent the sun's place; whose distance from earth could be accurately determined, by taking the known diameter of the earth for our

measuring unit. This plan is illustrated by the diagram below, which I will describe as follows:

S

The circle represents the earth, the line E, the equator, and A my place of observation in lat. 43° north, while s indicates the point where the line C, (representing the sun's rays,) intersects the earthperpendicular line D, which point locates the sun; and a, B, C, is the angle which the sun-rays make with the line B, which is perpendicular to my place of observation.

E

B

that distance.

Taking this as the basis of calculation, it is evident that the distance from earth to s. would be as many times the earth's diameter (7926 miles) as its diameter is contained in

After this plan had been carefully considered, diagrammed, and settled upon, I confidently awaited the 23d. of September,

earnestly hoping it might be a clear day, and conditions favorable for me to gather data for making this positive mathematical calculation of a quantity which, I had been led to believe, had in the past been computed by very uncertain methods.

TAKING THE SUN'S ALTITUDE.

The eventful day came at last, and everything seemed to favor the momentous undertaking. The sky was without a cloud, and to my great satisfaction, the family all went to town that day, except my crippled uncle, who sat in his great easy chair, no doubt wondering what strange freak the boy was pursuing again, while I made my elaborate. preparations for "taking the sun's altitude" when it should reach its meridian height, as its rays came in over the window-sill and rested on the floor of the living-room which we occupied.

My observation was duly made, and satisfactory results obtained, which I very soon applied to the diagram that had previously