PEEFACE TO THE FIRST EDITION. 



The rapid advances which have been made in modern times, 

 towards a correct knowledge of the intimate structure of 

 animate and inanimate beings, by the employment of the 

 Microscope, have given to this instrument an importance 

 second only to that of the Telescope. By its agency alone 

 have crude notions and theories been swept away, and science 

 in civilized countries made to stand on a firmer basis. In this 

 land of machinery and manufactures, artists have not been 

 found wanting to devote their time and talents to the conver- 

 sion of what might once have been an amusing instrument or 

 a toy, into one of the most powerful auxiliaries that can be 

 employed in scientific research. In proportion to its use, so 

 has been the demand for improvement in its construction, and 

 both amateur and optician have laboured together to bring it 

 to its present state of perfection, the former, in many cases, 

 furnishing the means to enable the latter to carry out his 

 designs. In the present day, so urgent has been the call for 

 Achromatic Microscopes in England, that the demand has far 

 exceeded the supply of information on matters connected 

 with their construction and use; since the works of Sir D. 

 Brewster, Ur. Goring, and Mr. Pritchard, no treatises of a 

 practical nature have been published in this country. The 

 writings of Mr. Pritchard, although very excellent, are chiefly 

 confined to the instruments and apparatus of his own manu- 

 facture; consequently, persons who are in possession of 

 microscopes constructed by others (and these by far the 

 most numerous class) are still without a guide to their 



