Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/436

 trary, the Tide is the cause of them, that is, of bringing them into the brains more apt for loquacity and ostentation, than for the speculation and discovering of the more abstruse secrets of Nature; which kind of people, before they can be brought to pronounce that wise, ingenious, and modest sentence, I know it not, suffer to escape from their mouths and pens all manner of extravagancies. And the onely observing, that the same Moon, and the same Sun operate not with their light with their motion, with great heat, or with temperate, on the lesser reeeptacles of Water, but that to effect their flowing by heat, they must be reduced to little lesse than boiling, and in short, we not being able artificially to imitate any way the motions of the Tide, save only by the motion of the Vessel, ought it not to satisfie every one, that all the other things alledged, as causes of those effects, are vaine fancies, and altogether estranged from the Truth. I say, therefore, that if it be true, that of one effect there is but one sole primary cause, and that between the cause and effect, there is a firm and constant connection; it is necessary that whensoever there is seen a firm and constant alteration in the effect, there be a firm and constant alteration in the cause. And because the alterations that happen in the ebbing and flowing in several parts of the Year and Moneths, have their periods firm and constant, it is necessary to say, that a regular alteration in those same times happeneth in the primary cause of the ebbings and flowings. And as for the alteration that in those times happens in the ebbings and flowings consisteth onely in their greatness; that is, in the Waters rising and falling more or lesse, and in running with greater or lesse impetus; therefore it is necessary, that that which is the primary cause of the ebbing and flowing, doth in those same determinate times increase and diminish its force. But we have already concluded upon the inequality and irregularity of the motion of the Vessels containing the Water to be the primary cause of the ebbings and flowings. Therefore it is necessary, that that irregularity, from time to time, correspondently grow more irregular, that is, grow greater and lesser. Now it is requisite, that we call to minde, that the irregularity, that is, the different velocity of the motions of the Vessels, to wit, of the parts of the Terrestrial Superficies, dependeth on their moving with a compound motion, resulting from the commixtion of the two motions, Annual and Diurnal, proper to the whole Terrestrial Globe; of which the Diurnal conversion, by one while adding to, and another while substracting from, the Annual motion, is that which produceth the irregularity in the compound motion; so that, in the additions and substractions, that the Diurnal revolution maketh from the Annual motion,