The Practical Teacher Volume 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1883 Excerpt: ...give way to some yet mightier power; gas is being superseded by a better method of lighting, but no agency can ever excel that which is instantaneous. Here, for the first time, the human mind has reached the utmost limit of its progress. The union of distant localities by telegraph has quickened the interest which men have in the concerns of each other, and has roused an ever-increasing eagerness for news. The use of the telegraph for informing the Government of what is transpiring at home, in the Colonies, or in foreign countries, cannot be overestimated. The merchant uses it in every branch of his business; in short, it would be difficult to mention where the telegraph is not useful for speedy conveyance of every kind of intelligence. The telephone has added still more to the power of this wonder of our age. o r A E From the point A in the diameter DE of the semicircle DBC, let the two lines AB.AC be drawn, namely AB to B (the middle point of thearc ABC, ) and AC at right angles to DE. Then the squares on AB, AC, shall be together double of the square on the radius, i.e., on FB. Since B is the middle point of the arc DBE, FB is evidently at right angles to DE; therefore the sq. on BA = sq. on BF + sq. on AF but the sq. on CA= sq. on FC-sq. on AF by add... the sq. on BA + sq. on CA = sq. on BF + sq. on FC that is, the sqs. on BA and CA= twice the sq. BF (the radius). r V T- 2. If a straight line be divided into any two parts, the rectangle contained by the whole and one of the parts is equal to the rectangle contained by the two parts, together with the square on the aforesaid part. (Prop. 3, Book II.) 3. In every triangle, the square on the side subtending either of the acute angles is less than the squares on the sides containing that angle by twice ..