Milky Way. S3l 



method he followed has acquired great celebrity from its re- 

 sults. It was, besides, very simple, and consisted, according to 

 the picturesque expression of the illustrious author, in gauging 

 the heavens. 



In order to determine the comparative mean richness in stars 

 of any two regions of the firmament, the observer made use of a 

 telescope whose field embraced a circle of fifteen minutes di- 

 ameter. Towards the middle of the first of these regions, he 

 counted successively the number of stars included in ten fields 

 contiguous, or at least, very near each other. He added 

 these numbers, and divided the sum by 10, The quotient 

 was the mean richness of the region explored. The same 

 operation, the same numerical calculation, gave him an analo- 

 gous result for the second region. When this last result was 

 double, triple, — decuple the first, he legitimately deduced the 

 consequence from it, that in an equal extent, one of these 

 regions contained twice, three times, or ten times more stars 

 than the other ; that it presented a condensation, a degree of 

 richness, double, triple, decuple. 



The gauging tables, or soundings of the firmament, which 

 form part of a memoir printed in 1785, in the 75th vol. of the 

 Phil. Trans., present regions where the mean number of stars 

 embraced in the field of Herschel's telescope was only 5, 4, 

 3, 2, and 1. We even find some among which at least four 

 successive fields were required to meet with three stars. Else- 

 where, on the contrary, these fields, although so restricted, — 

 these circular areas of 15' diameter, — contained 300, 400, 500, 

 and even 588 stars ! When the telescope was directed to- 

 wards the most thickly peopled regions, the eye, applied to the 

 glass, saw, in the short interval of a quarter of an hour, 116,000, 

 stars ! These numerical results are truly prodigious. The 

 word prodigious, in relation to the number 116,000, will seem 

 no exaggeration to any one who knows that the stars visible 

 to the naked eye throughout the whole nights of the year, do 

 not exceed about 5000, and that the ancients were acquaint- 

 ed with only 1022. The word will appear equally natural if 

 we apply it to the 400, 500, and 600 stars seen simultaneous- 

 ly in the telescope, provided it be kept in mind, that, with a 

 diameter of 15', the field of the instrument embraced only a 

 fourth part of the apparent surface of the sun. 



