SECT. XXXII. 6. i. OF IRRITATION. 293 



neoufly relieve thofe nervous pains, which attend the cold peri- 

 eds of hyfteric, afthmatic, or epileptic difeafes ; and that even 

 where large dofes of opium have been in vain exhibited. In 

 thefe cafes the pulfe becomes ttronger after the bleeding, and 

 the extremities re ain their natural warmth ; and an opiate then 

 given ats with much more certain effe<fi. 



VI. There is another caufe, which feems occafionally to in- 

 duce quicfcence into fome part of our fyftem, I mean the influ- 

 ence of the fun and moon ; the attraction of thefe luminaries, 

 by decreafing the gravity of the particles of the blood, cannot af- 

 fec.1 their momentum, as their vis inertiae remains the fame ; 

 but it may neverthelefs produce fome chemical change in them, 

 becaufe whatever affecls the general ai tractions of the particles 

 of matter may be fuppofed from analogy to afreet their fpecific 

 attractions or affinities : and thus the Stimulus of the particles 

 of blood may be diminished, though not their momentum. As 

 the tides of the fea obey the fouthing and northing of the moon 

 (alloxving for the time neceffary for their motion, and the ob- 

 ftruclions of the fliores), it is probable, that there are alfo at- 

 moipheric tides on both fides of the earth, which to the inhab- 

 itants of another planet might fo deflect the light as to refemble 

 the ring of Saturn. Now as thefe tides of water, or of air, are 

 raifed by the diminution of their gravity, it follows, that their 

 prefTure on the furface of the earth is no greater than the prefTure 

 of r he other parts of the ocean, or of the atmofphere, where no 

 fuch tides exilt ; and therefore that they cannot affect the mer- 

 cury in the barometer. In the fame manner, the gravity of all 

 other terreltrial bodies is diminished at the times of the fouth- 

 ing and northing of the moon, and that in a greater degree when 

 this coincides with the fouthing and northing of the fun, and 

 this in a Hill greater degree about the times of the equinoxes. 

 This decreafe of the gravity of all bodies during the time the 

 moon pafles our zenith or nadir might poflibly be (hewn by the 

 flower vibrations of a pendulum, compared with a fpring clock, 

 or with agronomical obfervation. Since a pendulum of a cer- 

 tain length moves flower at the line than near the poles, becaufe 

 the gravity being diminished and the vis inertiae continuing the 

 fame, the motive power is lefs, but the refiftance to be overcome 

 continues the fame. The combined powers of the lunar and 

 folar attraction are eftimated by Sir Ifaac Newton not to exceed 

 one 7,868,8501!! part of the power of gravitation, which feems 

 indeed but a fmall circumStance to produce any confiderable ef- 

 fecT: on the weight of fublunary bodies, and yet this is fufficient 

 to raife the tides at the equator above ten feet high ; and if it be 

 considered, what fmall impulfes of other bodies produce their 



effefts 



