eccentricity, that is the distance between its foci, the pins.

2. We cannot give figures in our periodical, but any person can draw the curve from the above description of it; and all the planets move in ellipses, with the sun in one of the foci. How do we know this? I shall endeavour to explain the mode of the discovery.

3. The ancients believed that the planets moved in circles, with the earth in the centre common to them all. Now an ellipse (as we have seen) may be very nearly circular, and as their conjecture agreed with general appearances, their belief was a very natural

one.

4. As far as mere vision is concerned, it would be impossible to say whether the sun moved round the earth, or the earth round the sun, because appearances would be precisely the same in either case; nay we ourselves, though we have decided that the earth revolves in an ellipse with the sun in one focus, usually speak of the solar orbit, the sun's mean motion, and so forth.

5. Speaking then according to appearances, we may reason thus. If the sun moved in a circle, the earth occupying its centre, his distance from us would be invariable, and consequently his apparent magnitude always the same; but in measuring his angular diameter, it is found to vary, therefore his distance varies. Again, there is a law of attraction which would cause one body to revolve round another in a circle, but then the velocity of the moving body would be uniform. Now by comparing the sun's daily motion in his orbit, we find his rapidity alters; both these circumstances shew, that the earth cannot describe a circle round the sun, nor the sun round the earth.

6. The reader will take two things for granted; first that, under a given supposition, we can compute the

place of a heavenly body, and next, that with a properly mounted telescope we can observe its place, and thus tell whether the fact agrees with the computation. For example, let it be supposed that the planet Mars moves round the sun in a circular orbit, the sun being its centre: then the astronomer begins his observations; from these he gets certain facts, relative to the elements of the orbit; he then computes the place of Mars for some future time; he observes the planet at that time: if his observed place agree exactly with the computed, he has good reason to rest satisfied that Mars does so move in a circle; if not, he begins to seek or conjecture some new theory of the planet's motion.

7. Thus did Kepler, a famous astronomer of the 16th century. He watched Mars with the most constant assiduity, and worked out his computations with incredible labour. He assumed the planet to move in a circle, having the sun in the centre, but the calculated place did not agree with the observed. He next tried the supposition of a circle, with the sun a little removed from the centre; still the result on paper differed from the result of the telescope. He then guessed an ellipse with the sun in one focus, and was delighted to find that now the computed plan agreed almost to a nicety with the observed. Having found this true for Mars, he concluded it true for all the planets, and every combination of calculation and observations confirmed the theory. Such is the history of the discovery of elliptical motion; it gave rise to much that we must pass by, as being too purely mathematical.

8. If then the earth moves round the sun in an ellipse, the sun occupying one focus, the sun's apparent diameter would change, and his velocity in his apparent orbit would vary: they would also both vary according to a known law. Now they are both capable of being measured, and are actually found to change as

they ought to do, by the elliptic theory, which is indeed the confirmation of the theory.

9. In point of fact, the orbits of most of the planets are so nearly circular, that on a sheet of paper they may be drawn as circles; with the earth (for instance) the eye would not detect the deviation from its orbit's circular form but to be correct, the reader must modify the statement given in our preceding article, (for January,) and instead of circles, must draw ellipses, taking the mean distances as then stated.

:

10. The eccentricity is expressed in parts of the mean distance; thus dividing such distance into thousandths, the eccentricities are nearly as follows: Mercury 205, Venus 6, the Earth 16, Mars 93, Jupiter 48, Saturn 56, that is, in the case of the Earth, the distance between the pins would be only sixteen thousandths of the major axis, so near is it to a circle, and the orbit of Venus is yet more circular.

11. If the sun and the earth were the only bodies in our system, the earth would describe a perfect ellipse round the sun; but the same law of attraction which operates in these two bodies, acts equally in all the rest; so that all the planets mutually disturb each other's true elliptic motion. This is called the theory of perturbations, and its consequence is, that no planet describes a perfect ellipse, though the deviation from it may be very small.

12. If therefore the reader will draw or imagine the planetary orbits, with the sun in one focus common to them all, and round this system on every side, at immense distances, will conceive the firmament of the fixed stars, he will form so far a correct idea of the starry heavens, adding however the moon in an ellipse with the earth in its focus, and Jupiter and Saturn with their several moons, moving round them in orbits elliptical.

(To be continued.)

(53)

ON DISTRICT VISITING.

(Concluded from last month.)

The regular system of lay help, under the sanction and authority of our bishops, is not at present to be looked for, though the large population of many parishes calls for such aid. The primitive churches, and our own church abroad, are examples of its lawfulness and expediency; but, until it is duly organized, each clergyman (if he sees fit) can get some help in the ordinary system of district visiting.

Our visitors are usually women, men have less leisure, and less willingness; nay, as friendly visitants, females are in some respects preferable to the other sex, for there is much domestic want, which they are better able to understand and relieve, when it comes under their notice in visiting.

Again, if the visitors are chiefly women, so are those they call on. The husband is out at work, or engaged in his daily occupation; it is the wife and children that will generally be found at home, so that the fitness of the sex for the employment commends itself to every mind.

Some persons object to the system altogether; and there are texts about "busy bodies," and common-place wit about 'women's tongues,' that are made to bear out such objections. But this is unworthy of the gravity of christian truth, as it is opposed to ancient christian practice; to visit the afflicted or poor, is a work honored and accepted by Christ, and it belongs not to men more than to women.

Another objection is that it usurps a spiritual office. This is not the case, I never heard of any such usurpation; the visitors do not baptize children, or administer the holy supper: but if any shall speak about bible topics, or read God's holy word, this is doing no more

than every christian is exhorted to do. On this point the clergy need have no jealousy, and when their visitors are discreet, sound minded persons,'no fear. How strange it would seem, if we had no fear of silly trifling conversation among our parishioners, but were frightened if we heard that such an one had read the Scriptures to this sick woman, or offered a prayer at the bedside of that afflicted child. To leave the church communion, and set up as teachers in another sect, is presumptuous and sinful; but why the members of our own community are to be tongue-tied in religious matters, I cannot perceive. But one thing must be noticed, this plea has nothing to do with a society: my argument is that each christian, by himself, and on his own account, is encouraged by the New Testament to visit the widows or the afflicted, to speak for comfort and instruction, to read the scriptures, and join in or offer up prayer, by a sick person's bedside, by the very constitution of our unity and christian brotherhood: all this belongs to no special office, but is common to all the members of Christ's body. So that a 'Society,' (by which I mean an arrangement for the division of a parish, and the orderly allotment of such a part to such a person's care,) is a mere matter of wisdom and convenience, and does not touch the question; it confers no new powers, and takes away no previous privileges or duties.

But it would as a system work badly, says one! It would gender schisms, and lower the position of the authorized minister! I think not. To say that some defects or faults may appear in it, is in other words only saying it is human; but if the visitors are all of one communion, I cannot see how the evils named are likely to follow. Women are not likely to make sects, less so than men. Suppose you say that a young man who had been much occupied as a catechist or reader would