Father. Philosophy is a word which in its original sense signifies only a love or desire of wisdom; and you will not allow that you and your brother are too young to wish for knowledge.

Emma. So far from it, that the more knowledge I get the better I seem to like it; and the number of new ideas which, with a little of your assistance, I have obtained from the "Evenings at Home," and the great pleasure which I have received from the perusal of these volumes, will, I am sure, excite me to read them again and again.

Father. You will find very little in the introductory parts of natural and experimental philosophy, that requires much more of your attention than many parts of that work with which you have been so delighted.

Charles. But in some books of natural philosophy, which I have occasionally looked into, a number of new and uncommon words have perplexed me; I have also seen references to figures by means of large letters and small, the use of which I did not comprehend.

Father. It is frequently a dangerous practice for young minds to dip into subjects before they are prepared, by some previous knowledge, to enter upon them; since it may create a distaste for the most interesting topics. Thus those books which you now read with so much pleasure would not have afforded you the smallest

entertainment a few years ago, when you must have spelt out almost every word in each page. The same sort of disgust will naturally be felt by persons who attempt to read works of science before the leading terms are explained and understood. The word angle is continually recurring in subjects of this sort, do you know what an angle is?

Emma. I do not think I do; will you explain what it means?

Father. An angle is made by the opening of two straight lines. In this figure (Plate 1. Fig. 1.) there are two straight lines AB and CB meeting at the point B, and the opening made by them is called an angle.

Charles. Whether that be small or great, is it still called an angle?

Father. It is; your drawing compasses may familiarize to your mind the idea of an angle; the lines in this figure will aptly represent the legs of the compasses, and the point B the joint upon which they move or turn. Now you may open the legs to any distance you please, even so far that they shall form one straight line; in that position only they do not form an angle. In every other situation an angle is made by the opening of these legs, and the angle is said to be greater or less, as that opening is greater or less.

• Straight lines, in works of science, are usually denominated right lines.