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the stars; he discovered that the period of 365 days 6 hours, which had been considered as the true length of the solar year, was too great by about 5 minutes, and observed that the four parts, into which the year is divided by the solstices and equinoxes, are by no means equal, the sun occupying 941 days in passing from the vernal equinox to the summer solstice, and only 92 from the same solstice to the autumnal equinox, and that therefore the sum remained 187 days in that part of the ecliptic which lies north of the equator, and only 178 in the other part.”
Laplace concludes that the mean heat of the earth cannot be altered by lo of Reaumur since the time of Hipparchus, inasmuch as the dimensions of the globe would be thereby changed in a small amount, its angular velocity increased or diminished, and a sensible difference be made in the length of the day—and this is found not to be the case.
On the subject of Eclipses. There is no phenomenon connected with the appearances and motions of the heavenly bodies which creates so much astonishment among those who have never thought on the subject, as an eclipse of the sun or moon ; and that the time of its having happened, or of its happening for the future, can be so exactly computed, is a subject of no less wonder.
It is familiar to every one, that an opaque body of sufficient size may be so placed between a luminous body and the eye of an observer, as to stop all the light proceeding from it, and in this case the luminous body becomes invisible,
Now an eclipse happens in consequence of one of the opaque bodies, the earth and the moon, being so placed as to prevent a light falling upon the other.
The moon coming between the sun and earth causes an eclipse of the sun, and this happens at new moon, when she is between the earth and sun, and hinders the rays of light from falling upon the earth.
The earth coming between the sun and moon causes an eclipse of the moon, and happens at the same instant of absolute time to all observers, longitude calculated from this.
The shadow of the earth or moon is conical, having the area of a great circle for its base. The length of the earth's shadow is 216-511 semi-diameters of the earth.
What is meant by the transit of a planet over the sun's disc? How is it that the transit of Mercury, on the 9th of November, 1848, could not be seen to its termination by an observer in Paris, but would by one in Ireland ?
Facts of this kind, when understood, many of which they will be able afterwards to verify by their own observation, will to many, I have no doubt, be a source of rational enjoyment in their homes, and make them feel that they belong to a class of beings of an intellectual kind; instead of being unmoved or stupefied by the grandeur of the appearances about them, they will turn their thoughts to that God who made them, and call to mind the lessons they have learned at school in their childhood,
Child of the earth! O lift your glance
Yet fear not thou - the sovereign hand,
CHEMISTRY. The subject of Chemistry is one which may be made both interesting and useful, perhaps more so than almost any other of a secular kind, in the class of schools for the teachers of which these pages are written, whether in towns or in the rural districts.
About two years ago, the subject of chemical agriculture was introduced in this school, witli Professor Johnston's Catechism as a text-book, and sufficient apparatus for the experiments required to illustrate it. What has been done and the way in which it has been received, is a sufficient proof, that instruction in this might form an important feature at the larger class of schools in our rural districts, where the teachers are qualified to give it, or where those interested in the school have an inclination to introduce it; this would attract the attention of the farmer as regards his own children, not that I think that is wanted; when the education in our parish schools is in other respects good, they will, in the end, avail themselves of it. The difficulty is in finding qualified teachers, but let them once be properly remunerated, and society made to feel and estimate at its proper value the real worth of a sound practical education, preparing them for the duties of this life as well as for a future existence, this difficulty will cease, and qualified teachers will soon be found : nor is it too much to expect from the most advanced nation in the world, as to its political and social constitution, science, and wealth, that it should grant a liberal allowance to the education of its youth: were it to do so, the gain, even in a pecuniary point of view, would in the end be great, independent of those moral considerations which ought never to be lost sight of.
The first object of the farmer is to produce food for man and beast in the cheapest way he can—to get the most productive crops, at the least possible expense; and although experience is not to be despised, yet assisted by science, much more may be done than without it- this it is difficult to persuade the farmers; some knowledge of manures, they think, may be of service, but beyond the “Muck Manual,” in the way of book-learning, very few of them are inclined to gostill they are on the march, and when they see their way, through experiments successfully tried, prejudices will give way; there is something of wisdom in not abandoning a tolerably good plan, unless you have confidence in the one which is recommended being better, and the road to confidence is practical proof.
One of the first questions naturally would be of what are all these plants composed ?--On inquiry, they are all found to consist of two classes of substances, varying with different plants, one of which is volatile, called organic, the other, which remains after combustion, in the form of ashes, and called inorganic-these again are analysed into their separate elements, and it is thus seen what the plant is made up of.
Now, it is evident, that the seed, after it is sown and germinates, as well as grasses, during their growth, cannot find such substances as they are composed of, the crop must necessarily be an unproductive one, and that in proportion to the deficiency of the substances required. The next question is
Where are they to find all the things which enter into their composition ? - which of them can be supplied by the industry of the farmer? --and which of them must he trust to atmospheric influences to supply?
To this, science gives an answer—the farmer judges from experience-- the agricultural chemist would analyse the soil, and find out its separate elements — he knows the elements of the crop he wants to grow, and knowing which of these are to be found in the soil, and for which he must trust to the atmosphere, he would use that kind of manure which would supply the rest—and that such substances as any particular crop is known to take away, must be supplied in the shape of manure, otherwise the land will be worn out.
A knowledge of the particular substances which a crop of any kind, as wheat, barley, etc., takes out of the ground, and of what is wanted by the crop which is intended to follow would point out a good rotation of cropping; and, in addition to this, knowing the composition of the soil, would lead to a proper economy in not casting useless substances on the land as manure - such substances as did not contain the particular things wanted. · This does not apply merely to grain crops, but to all others; and although long experience may have taught the farmer a right course as to the ordinary crops; yet, take the case of a new plant, a grass, or other plant which is recommended, he is then at a loss as to the soil he ought to try it in; he therefore goes by guess — if he hits upon a favourable soil he pronounces in its favour; if not, it is condemned; and it will only be after a long time, and after many successful or unsuccessful trials and much expense, that it is found out what soil will suit this plant and what will not. Now, here science might help to a speedier and less expensive mode of trying it-burning the plant, examining the ashes, and analysing the soil in which it is intended to to be tried, would shew whether they suit each other or not.
Thus, science, with caution, may at once point out a right course, when it would take years of experience to find it out.
Then again, with respect to manures, although a substance thrown on the ground may contain the ingredient wanted, it may not contain it in such a form that the plant can avail itself of it. Here, again, science steps in, and teaches that the nourishment which plants take up by the roots must necessarily be in a fluid form that they cannot assimilate to themselves any substance in a solid state ; although it may be the very thing they like best, and therefore it will be necessary to use such manures as are soluble in water – by the rains which fall, or which, from exposure to the atmosphere, become so—that after decomposition every animal and vegetable substance returns in one shape or other--the organic parts through the atmos. phere in a gaseous form — the inorganic as solid substances thrown upon the ground, for the future nourishment of plants, and through them, of animals.