PORTION OF THE COSMOS. NEBULA. 255 



" the Milky Way appears bright because it consists of denser 

 celestial matter, and therefore radiates more light, so the 

 dark patches which are not seen in Europe are entirely 

 without light, because they form a region of the heavens 

 which is void, i. e., composed of very rare and highly 

 transparent matter." That a celebrated astronomer should 

 have identified this description with the solar spots ( 449 ) is 

 no less strange than that the missionary Bichaud (1689) 

 should have taken Acosta's "Manchas negras" for the 

 luminous Magellanic Clouds ( 45 ). 



Bichaud, like the oldest navigators, speaks of the " coal- 

 sacks" in the plural j he names two, one in the Cross, and 

 another in Bobur Caroli : in other descriptions this last is 

 even divided into two separate spots or patches. These are 

 described by Eeuillee in the first years of the 18th century, 

 and by Horner in a letter written to Olbers from Brazil in 

 1804, as imperfectly defined and with confused edges ( 451 ). 

 During my stay in Peru I never could make out in a manner 

 satisfactory to myself the Coal-sacks in Bobur Caroli, and 

 being disposed to attribute my want of success to the low 

 altitude of the constellation, I turned for information and 

 instruction on the subject to Sir John Herschel, and to the 

 Director of the Hamburgh Observatory, Hr. Bumker, both 

 of whom had been in much higher southern latitudes. I 

 found that notwithstanding all their endeavours neither of 

 these gentlemen had ever succeeded any more than myself 

 in finding anything which for definiteness of outline or in- 

 tensity of blackness could be compared to the " Coal-sack" 

 in the Cross. Sir John Uerschel thinks that we ought not to 

 speak of a plurality of coal-sacks unless we intend to regard 



