VISIBILITY OF STAE3. 73 



that stars might occasionally be seen from caverns and cisterns, 

 as through tubes. Pliny alludes to the same circumstance, 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 observe 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 day-light ; although in the many latitudes, in 

 both hemispheres, in which I have visited deep mines, a suffi- 

 ciently large number of stars must have passed the zenith to 

 have afforded a favourable 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 day-light, through the shaft of a chimney. 2I 



differences of colour, although he will see objects at a greater 

 distance. Hence it arises that persons in caverns or cisterns 

 are occasionally enabled to see stars" The Grecian 'Opuy/zara, 

 and more especially <pe'ara, are, as an eye-witness, Pro- 

 fessor Franz, observes, subterranean cisterns or reservoirs 

 which communicate with the light and air by means of a 

 vertical shaft, and widen towards the bottom, like the neck 

 of a bottle. Pliny (lib. ii. cap. 14) says, "Altitudo cogit 

 minores vicleri Stellas ; atfixas coelo solis fulgor interdiu non 

 cerni, quum aaque ac noctu luceant ; idque manifestum fiat 

 defectu solis et prtealtis 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 

 aii'/' 



21 " We have ourselves heard it stated by a celebrated opti- 

 cian 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 questioned agree 



