Scientific Lectures. 19 



acquire almost all tlie knowledge we possess of tlie material objects 

 bv wliicli we are surrounded. And as it is by taking advantage of 

 these properties that the instrument is made to accomplish the object 

 proposed in its cOTstruction, so it is out of these properties themselves 

 that the difRculties arise which embarrass its construction, and which 

 have made its progress toward its present high degree of perfection 

 laborious and slow. 



But it is not as an illustration of optical science, or as an example 

 of the ingenious adaptation of means to ends, or as a proof of the 

 exquisite perfection of mechanical art in our time, that the microscope 

 is principally interesting. If this were so, we should have no 

 microscope at the present worthy of the name. Beautiful as is the 

 instrument itself, and surprising as is the insight it gives us into a 

 world imperceptible to ordinary vision, it would never have enlisted, 

 in the effort for its improvement the persevering labors of so many 

 able men or accomplished artists but for the fact that its perfection 

 was sought for not as an end, but as a means. In the study of the 

 works of nature, it is but a narrow range which our unassisted senses 

 enable us to grasp. If we look abroad from our planet into space, 

 there is not one of the brilliant objects which stud the heavens, of 

 which the information furnished by simple vision enables us to form 

 the slightest conception. Their dimensions, t]?.feir motions, their 

 distances, the features of their surfaces,, their enveloping atmospheres 

 all these things are matters of wliich our natural powers permit us to 

 discover nothing whatever. It is not, therefore, by any means 

 surprising that, in an age when the telescoj^e had not been dreamed 

 of, the sky should have been taken for a transparent vault, and the 

 heavenly bodies should have been supposed to be attached to its 

 surface, like gems set in a crystal goblet. In like manner, if we 

 attempt to survey objects of considerable dimensions on the earth's 

 surface, we reach very shortly the limit of our powers. Though we 

 discern the general outline of a mountain, we gather very little of the 

 detail of its form or its structure. Of an extended lake or valley, 

 the sight tells us still less. And, though this is the most perfect of 

 all our senses, we very soon find that a principal condition of its 

 usefulness is that its objects shall be of moderate dimensions and 

 near at hand. 



But even when this condition is realized, and objects are placed 

 immediately before us in the most advantageous light and under the 

 most favorable circumstances, we presently discover that there are 



