AEROLITES. 121 



should they not likewise, in obeying the laws of mutual at- 

 traction, blend together under definite relations of mixture, 

 composing the white glittering snow and ice in the polar 

 zones of the planet Mars, or constituting in the smaller cos- 

 mica! masses mineral bodies enclosing crystals of olivine, au- 

 gite, and labradorite ? Even in the domain of pure conjecture 

 we should not suffer ourselves to be led away by unphiloso- 

 phical and arbitrary views devoid of the support. of inductive 

 reasoning. 



Remarkable obscurations of the sun's disc, during which 

 the stars have been seen at mid-day (as for instance in the 

 obscuration of 1547, which continued for three days, and 

 occurred about the time of the eventful battle of Miihlberg), 

 cannot be explained as arising from volcanic ashes or mists, 

 and were regarded by Kepler as owing either to a materia 

 c&metica, or to a black cloud formed by the sooty exhalations 

 of the solar body. The shorter obscurations of 1090 and 

 1203, which continued the one only three and the other six 

 hours, were supposed by Chladni and Schnurrer to be occa- 

 sioned by the passage of meteoric masses before the sun's 

 disc. Since the period that streams of meteoric shooting 

 stars were first considered with reference to the direction of 

 their orbit as a closed ring, the epochs of these mysterious 

 celestial phenomena have been observed to present a remark- 

 able connection with the regular recurrence of swarms of 

 shooting stars. Adolph Erman has evinced great acuteness 

 of mind in his accurate investigation of the facts hitherto 

 observed on this subject, and his researches have enabled him 

 to discover the connection of the sun's conjunction with the 

 August asteroids on the 7th of February, and with the No- 

 vember asteroids on the 12th of May, the latter period 

 corresponding with the days of St. Mamert (May llth), St. 

 Pancras (May 12th), and St Servatius (May 13th), which r 

 according to popular belief, were accounted " cold days."* 



* Adolph Erman, in Poggend. Annalen, 1839, bd. xlviii. s. 582-601. 

 Biot had previously thrown doubt regarding the probability of the No- 

 vember stream reappearing in the beginning of May (Comptes JRendus, 

 1836, t. ii. p. 670). Madler has examined the mean depression of tempera- 

 ture on the three ill-named days of May by Berlin observations for 8$ 

 years ( Verhandl. des Vereim zur Beford. des Gartenbaues 1834, s. 377), 

 and found a retrogression of temperature amounting to 2'2 F. from the 



