VISIBILITY OF STARS. 57 



that stars might occasionally be seen from ctverns and cis- 

 terns, as through tubes. Pliny alludes to the same circum- 

 stance, and mentions the stars that have been most distinctly 

 recognized during solar eclipses. While practically engaged 

 in mining operations, I was in the habit, during many years, 

 of passing a great portion of the day in mines where I could 

 see the sky through deep shafts, yet I never was able to ob- 

 serve a star ; nor did I ever meet with any individual in 

 the Mexican, Peruvian, or Siberian mines who had heard of 

 stars having been seen by daylight ; although in the many 

 latitudes, in both hemispheres, in which I have visited deep 

 mines, a sufficiently large number of stars must have passed 

 the zenith to have afforded a favorable opportunity for their 

 being seen. Considering this negative evidence, I am the 

 more struck by the highly credible testimony of a celebrated 

 optician, who in his youth saw stars by daylight through the 

 shaft of a chimney.* Phenomena, whose manifestation de- 

 pends on the accidental concurrence of favoring circum- 

 stances, ought not to be disbelieved on account of their 

 rarity 



The same principle must, I think, be applied to thv. asser- 

 tion of the profound investigator Saussure, that stars have 

 been seen with the naked eye in bright daylight, on the de- 

 clivity of Mont Blanc, and at an elevation of 12,757 feet 

 " Q,uelques-uns des guides m'ont assure avoir vu des etoiles 

 en plein jour ; pour moi je n'y songeais pas, en sorte que je 

 n'ai point ete le temoin de ce phenomene ; mais V assertion 

 uniforme des guides ne me laisse aucun doute sur la rea- 

 lite. II faut d'ailleurs etre entierement a l'ombre d'une epais- 

 seur considerable, sans quoi fair trop fortement eclaire fait 

 evanouir la faible clarte des etoiles." " Several of the guides 

 assured me," says this distinguished Alpine inquirer, " that 



cogit minores videri Stellas ; affixas coelo solis fulgor interdiu non cerni, 

 quum seque ac noctu luceaut ; idque manifestum fiat defectu solis et prce- 

 altis puteis." Cleomedes {Cycl. Theor., p. 83, Bake) does not speak of 

 stars seen by day. but asserts " that the sun, when observed from deep 

 cisterns, appears larger, on account of the darkness and the damp air." 

 * " We have ourselves heard it stated by a celebrated optician that 

 the earliest circumstance which drew his attention to astronomy was 

 the regular appearance, at a certain hour, for several successive days, 

 of a considerable star, through the shaft of a chimney." John Herschel, 

 Outlines of Astr., 61. The chimney-sweepers whom I have ques- 

 tioned agree tolerably well in the statement that " they have never seen 

 6tars by day, but that, when observed at night, through deep shafts, the 

 sky appeared quite near, and the stars larger." I will not enter upon 

 any discussion regarding the connection between these two illusions. 



C 2 



