The above will be looked upon as an unwarrantably bold assertion; but a careful study of, or attention to, what is taught in the most advanced works on the solar system, even in science generally, will show it to be perfectly true. It is not only true, but the consequences of its being true have been much more serious than will be readily believed. In our own endeavours to understand what we had been reading, we have seen that some of the notions presented to us were only half formed, and that they have led to theories being founded which could never have been entertained at all had they been thoroughly studied out. More than that, they have prevented the truth from being arrived at in the fundamental conceptions of the construction of the earth, and, as a natural consequence, of the whole solar system, perhaps even of the whole universe.

There are probably many, even a great many, people who have arrived at the same conclusions as we have, but as far as it has been in our power to search into the matter, we have met with no attempt from any quarter to put an end to this defect in the literature of science; perhaps because the work has the appearance of being too great to be readily undertaken, and also because it may be thought that there is little to be gained by it—as all is sure to be set right through time. But, as we believe that it will be beneficial immediately, in the case of the earth and solar system at least, we shall first attempt to show what are some of the defects alluded to, and then what knowledge may be acquired through their removal.

[CHAPTER I.]

Page
[ 18]The bases of modern astronomy. Their late formation
[ 19]Instruments and measures used by ancient astronomers
[ 20]Weights and measures sought out by modern astronomers
[ 20]Means employed to discover the density of the earth.
  Measuring by means of plummets not sufficiently exact
[ 21]Measurements with torsion and chemical balances more accurate
[ 22]Sir George B. Airy's theory, and experiments at the Harton colliery
[ 23]Results of experiments not reliable. Theory contrary to the Law of Attraction
[ 24]Proof by arithmetical calculation of its error
[ 26]Difficulties in comparing beats of pendulums at top and bottom of a mine
[ 27]The theory upheld by text-books without proper examination
[ 28]Of a particle of matter within the shell of a hollow sphere.
  Not exempt from the law of Attraction
[ 29]A particle so situated confronted with the law of the
  inverse square ofdistance from an attracting body. Remarks thereon
[ 31]It is not true that the attraction of a spherical shell
  is "zero" for a particle of matter within it

Before astronomers could begin to determine the relative distances from each other, and the relative dimensions and masses of the various members of the solar system, they had to establish scales of measurements appropriate to their undertaking. This entailed upon them, of course, the necessity of determining the form, the different circumferences and diameters, and the weight of the whole earth, as any other scales derived from the only available source, the earth, would have been too small to give even an approximate value of the measures and masses to be sought for.

History tells us that at least one attempt had been made, over two thousand years ago, to find the circumference and necessarily the diameter of the earth, but it says nothing of any to ascertain its weight. There may have been many to determine both diameter and mass, but we know nothing of them; and when we think seriously about this, we cannot help feeling somewhat surprised that no attempt had been made to find out the density and mass till more than a century after Sir Isaac Newton's discovery of the law of Attraction, or Gravitation, as it is more usually called. But perhaps this is an idea that could only occur to one who has been spoilt by witnessing, in great measure, the immense strides in advance that have been made during the nineteenth century in science of all kinds, and does not duly take into account the immense labour, and the incessant meeting with almost insurmountable difficulties, that astronomers have had to encounter and overcome between the birth of modern astronomy and the end of the eighteenth century. Indeed, the difficulties can hardly be looked upon as altogether overcome even yet, as efforts are still being made to find out the exact distance of the sun, and it is not impossible that some small difference may be found, plus or minus, in the density at present adopted for the earth of 5·66 times the weight of water.

The geometer who, more than two thousand years ago, set himself the task of measuring the circumference of the earth, is supposed to have made use of very much the same kind of implements as those employed by modern astronomers. He must have had a very fair instrument for measuring angles, and have known very well how to use it, seeing he was able to determine a value for the obliquity of the ecliptic which agrees so well with that established by modern science, its variations being, for what we know, taken into account; and for length or distance he would doubtless have some implement analogous to the metre, chain, foot-rule, or something called by other name that would, in those days, present facilities for selling a yard of calico. His operations would probably be as plain and simple as those applied to the measuring of a village green—for we are not told that he had any idea of there being any difference between the length of a degree of the meridian at the equator and one nearer either of the poles—and involved no hypotheses or theories, any more than modern operations have done.

When the time came for making efforts to ascertain the density of the earth, science seems to have employed the very simplest means it had at its disposal for attaining its object, and to have gone on refining its implements and operations in conformity with the lessons it went on learning while pursuing its self-imposed task. Every one who, even for recreation, has read a fair amount of the multitude of works and writings that have been published on Popular Astronomy—not to speak of text-books—knows that the first attempts were made by measuring the attraction of steep, or precipitous, mountains for plummets suspended in appropriate positions in their neighbourhood; then—evidently from knowledge acquired during these operations—by the attraction for each other of large and small leaden balls suspended on frames and torsion balances, which go under the name of the Cavendish Experiment; and afterwards by a refinement on this in using the Chemical Balance, where only one large and one small ball of metal are required. All these operations and their results are to be found described in works of various kinds, and are generally reduced to something like the following tubular form, which we reproduce in order to make more intelligible what we have just said, and that we may make a few remarks upon them.