49.(Pg. [90]) What circumstance is said to have given rise to the speculations of Newton, on the subject of gravitation?
CONVERSATION VIII.
ON THE EARTH.
OF THE TERRESTRIAL GLOBE. OF THE FIGURE OF THE EARTH. OF THE PENDULUM. OF THE VARIATION OF THE SEASONS, AND OF THE LENGTH OF DAYS AND NIGHTS. OF THE CAUSES OF THE HEAT OF SUMMER. OF SOLAR, SIDERIAL, AND EQUAL OR MEAN TIME.
MRS. B.
As the earth is the planet in which we are the most particularly interested, it is my intention this morning, to explain to you the effects resulting from its annual, and diurnal motions; but for this purpose, it will be necessary to make you acquainted with the terrestrial globe: you have not either of you, I conclude, learnt the use of the globes?
Caroline. No; I once indeed, learnt by heart, the names of the lines marked on the globe, but as I was informed they were only imaginary divisions, they did not appear to me worthy of much attention, and were soon forgotten.
Mrs. B. You supposed, then, that astronomers had been at the trouble of inventing a number of lines, to little purpose. It will be impossible for me to explain to you the particular effects of the earth's motion, without your having acquired a knowledge of these lines: in [plate 8. fig. 2.] you will find them all delineated: and you must learn them perfectly, if you wish to make any proficiency in astronomy.
Caroline. I was taught them at so early an age, that I could not understand their meaning; and I have often heard you say, that the only use of words, was to convey ideas.