INTRODUCTORY REMARKS. 



1. OF all philosophical instruments there are certainly none which 

 are more interesting, or which present greater claims to our admiration 

 than the Microscope.* Wherever we turn, within the precincts of our 

 own homes in meadow or moorland, hill or forest, by the lone seashore 

 or amidst crumbling ruins fresh objects of interest are constantly to 

 be found ; plants and animals, unknown to our unaided vision, with 

 minute organs perfectly adapted to their necessities ; with appetites as 

 keen, enjoyments as perfect as our own. In the purest waters, as well 

 as in thick, acid, and saline fluids, of the most indifferent climates, 

 in springs, rivers, lakes, and seas, often in the internal humidity of 

 living plants and animals, even in great numbers in the living human 

 body nay, probably carried about in the aqueous vapours and dust of 

 the whole atmosphere there is a world of minute, living, organised 

 beings, imperceptible to the ordinary senses of man. In the daily 

 course of life, this immense mysterious kingdom of diminutive living 

 beings is unnoticed and disregarded; but it appears great and astonish- 

 ing beyond all expectation, to the retired observer, who views it by the 

 aid of the microscope. In every drop of standing water, he very fre- 

 quently, though not always, discovers by its aid rapidly moving bodies, 

 from 1-96 to less than 1-2000 of a line in diameter, which are often so 

 crowded together that the intervals between them are less than their 

 diameter. If we assume the size of the drop of water to be one cubic 

 line, and the intervals, though they are often smaller, to be equal to the 

 diameter of the bodies, we may easily calculate, without exaggeration, 

 that such a drop is inhabited by, from one hundred thousand to one 

 thousand millions of such animalculae ; in fact, we must come to the 

 conclusion, that a single drop of water, under such circumstances, con- 

 tains more inhabitants than there are individuals of the human race 

 upon our planet. If further, we reflect on the amount of life in a 



From JjllKpOC; small, and (TKOTTf to to observe. 



