268 Dr. Herschel's Observations to investigate 
confined to a small space. These nodules, and ridges, on account 
of their being brighter than the general surface of the sun, and 
also differing a little from it in colour, have been called faculse, 
and luculi. 
Corrugations, I call that very particular and remarkable un- 
evenness, ruggedness, or asperity, which is peculiar to the lumi- 
nous solar clouds, and extends all over the surface of the globe 
of the sun. As the depressed parts of the corrugations are less 
luminous than the elevated ones, the disk of the sun has an 
appearance which may be called mottled. 
Indentations are the depressed or low parts of the corruga- 
tions ; they also extend over the whole surface of the luminous 
solar clouds. 
Pores are very small holes or openings, about the middle of 
the indentations. 
Any other terms I may hereafter use, will be sufficiently 
explained by the observations in which they occur. 
I shall now enter into an examination of all the phenomena 
that may be observed in viewing the sun through a good teles- 
cope, beginning with those that are most common ; a critical 
investigation of which will lead us gradually to such as are more 
intricate. 
It will be seen that I have brought my observations under a 
number of short heads, or propositions, such as my subject 
requires. The advantage of this method is, that the tendency 
of every observation will be immediately understood, while it is 
read ; whereas, had I arranged these observations in the order 
in which they were made, the mixture of the various points to 
be ascertained by them must have brought on a considerable 
obscurity ; and, in drawing conclusions from them afterwards, 
