LUNAR INFLUENCES. 479 



societies abound with examples of giddiness, malignant fever, somnambulism, 

 &c., having in the.ir paroxysms more or less corresponded with the lunar 

 phases. Gall states, as a matter having fallen under his own observation, that 

 patients suffering under weakness of intellect, had two periods in the month 

 of peculiar excitement ; and in a work published in London so recently as 

 1829, we are assured that these epochs are between the new and full moon. 



Against all these instances of the supposed effect of lunar influence, we have 

 little direct proof to offer. To establish a negative is not easy. Yet it were 

 to be wished that in some of our great asylums for insane patients, a register 

 should be preserved of the exact times of the access of all the remarkable 

 paroxysms ; a subsequent comparison of this with the age of the moon at the 

 time of their occurrence would furnish the ground for legitimate and safe con- 

 elusions. We are not aware of any scientific physician who has expressly 

 directed his attention to this question, except Dr. Olbers of Bremen, celebrated 

 for his discovery of the planets Pallas and Vesta. He states that in the course 

 of a long medical practice, he was never able to discover the slightest trace of 

 any connexion between the phenomena of disease and the phases of the moon. 

 In the spirit of true philosophy, M. Arago, nevertheless, recommends caution 

 in deciding against this influence. The nervous system, says he, is in many 

 instances an instrument infinitely more delicate than the most subtle apparatus 

 of modern physics. Who does not know that the olfactory nerves inform us 

 of the presence of odoriferous matter in air, the traces of which the most re- 

 fined physical analysis would fail to detect ? The mechanism of the eye is 

 < highly affected by that lunar light which, even condensed with all the power 

 > of the largest burning lenses, fails to affect by its heat the most susceptible ( 

 thermometers, or, by its chemical influence, the chloride of silver ; yet a small 

 portion of this light introduced through a pin-hole will be sufficient to produce 

 an instantaneous contraction of the pupil ; nevertheless the integuments of this 

 membrane, so sensible to light, appear to be completely inert when otherwise 

 affected. The pupil remains unmoved, whether we scrape it with the point of 

 a needle, moisten it with liquid acids, or impart to its surface electric sparks. 

 The retina itself, which sympathizes with the pupil, is insensible to the influ- 

 ence of the most active mechanical agents. Phenomena so mysterious should 

 teach us with what reserve we should reason on analogies drawn from experi- 

 ments made upon inanimate substances, to the far different and more difficult 

 case of organized matter endowed with life. 



In conclusion, then, it appears that of all the various influences popularly 

 supposed to be exerted on the surface of the earth, few have any foundation in 

 fact. The precession of the equinoxes, the accumulated effect of which ren- 

 dered necessary the alteration of the calendar, which produced the distinction be- 

 tween the old and new style, is a consequence of the moon's attraction combined 

 with that of the sun upon the protuberant matter around the equatorial parts of 

 the earth ; and the nutation of the earth's axis, and the consequent periodical 

 change of the obliquity of the ecliptic, is an effect due to the same cause. I 

 have on another occasion shown that the tides of the ocean are real effects 

 also arising from the combined attractions of the moon and sun, but chiefly of 

 the former. 



The precession of the equinoxes is a progressive annual change in the posi- 

 tion of those points on the firmament where the centre of the sun crosses the 

 ( equator on the 21st of March and the 21st of September. It has been ascer- 

 J tained by observation, and verified by theory, that these points move annually 

 <, on the ecliptic with a slow motion in a contrary direction to the apparent mo- I 

 * tion of the sun ; in consequence of which the sun, after each revolution of the J 

 ^ ecliptic, meets these points before that revolution has been completed ; conse- ( 



