100 STUDY OF NATURAL HISTORY 
Mutability in science only belongs to error: for 
truth, no less than nature, is unchanging ; whereas 
mutability, on the contrary, is a necessary accom- 
paniment of art, and is interwoven with its very 
excellence. 
(48.) There is an inexpressible satisfaction, an in- 
tellectual delight, in the pursuit of truth, which few 
but the philosopher can fully understand. This 
luxury of the soul, as it may well be termed, belongs 
more especially to the pursuit of natural science ; 
particularly to those branches which are usually 
termed demonstrative. The man who studies the 
forms of nature, has before him, so far as those 
forms are concerned, models of perfection. He has 
no need to suspect that others exist, in distant coun- 
tries, more perfect of their kind, than those before 
him, and which he should previously see and study. 
He has not to consult popular taste, ephemeral 
fashion, or arbitrary opinion, on the value or import- 
ance of his pursuits. He has before him truth: 
his sole business is to analyse all the parts and all 
the bearings of that truth, and make them known to 
the world. The models and materials of his study 
are divine ; and how much they exceed those of any 
human artist, will be manifested by a blade of grass, 
compared with which the most exquisite carvings in 
stone or ivory sink into insignificance. The calcu- 
lations of the astronomer, and the results of the 
chemist, are productive of much the same feelings. 
Truth indeed is but seldom attained, yet with su- 
perior minds this very difficulty serves but to 
increase the ardour of its pursuit. 
(49.) Another advantage, almost exclusively be- 
