পাতা:পদার্থবিদ্যাসার.djvu/৬৫

4ே, out. They are formed from springs of fountains, formed by vapours carried from off the surface of the sea, rixers, &c. te the ridges of mountains. These vapours, sinking through the crannies of the mountain till they meet with a straturn of earth or stone, or other ańhstance, of a nature sufficiently solid to contain them, continue lodged there until they are of sufficient capacity to form a reservoir, which finding a passage, forms a spring; and several of these uniting, at length constitute the source ofa -river. Pop., What am to understand by the ebb and flood of the sea, or the rising and failing of the tide, as it is coinnonly called? 3. Tut. That this amazing collection of waters rises every six hours inére or less, which is called flood ; and after a very short time of rest, falls again, which we call the elob. This motion of the sea continues rising for six hours from south to north ; and after Seening at the highest for about twelve minutes, is a sain six hôurs falhing from north to south, when it remains twelve minutes at rest be fore it rises again, Pup. W hat is the influence of the sum, in propoition to that of the moon, in attracting the waters of the earth? Tut. It is supposed to be about one-third that of the moon. Pup. What is meant by spring and neap tides, aud how are they occasioned 2 out. A spring tide is occasioned when the action of the gun and moon conspire together, as tat the titue of new and full unoon, when they are both upon the meridian, eithyr in con unction or in opposition ; and * then the tides, or the flux and reflux, are at their highe»t. but whem the sua aryd nuoon act crosswise, nr are ninety degrees asunder, the one tends to elevate the waters, while the other depresses them, and the tides will consequently be lessened in proportion to he dif. ferellee of their powers of attraction; and thus the neap tides are produced, which happen at the first and third quarters of the moon,