INTRODUCTION. 7 



the practical details of manipulation almost neces- 

 sarily precede an advance in natural knowledge, 

 and invariably promote and expedite true scientific 

 progress." 



But although manipulative skill is a very necessary 

 adjunct to microscopical research, an attainment of 

 the understanding of the general principles of action 

 at the outset, sometimes proves to be the most 

 arduous portion of the work, and very often is the 

 only impediment to success. Practice and perse- 

 verance, brought to bear upon previously gained 

 knowledge, are the only royal roads to manual 

 dexterity, and it thus becomes the duty of the 

 instructor to point out, not merely what path 

 ought to be taken, but the various pit-falls which 

 everywhere surround the beaten track, and how 

 best to avoid them. 



IV. On Microscopical Art. 



There are two ways in which microscopical 

 objects can be drawn so as to become useful records 

 of research. By the first of these, a rough dia- 

 grammatic representation may be made, without 

 reference to accuracy of form or size ; merely to 

 display the observer's views concerning the struc- 

 ture of the object. The second method is to make 

 an accurate drawing with due regard to the size and 

 form of the object under the microscope. Both of 

 these methods are valuable in themselves, but their 

 usefulness becomes immeasurably enhanced when 

 they are combined so as to afford scope to the 

 artistic skill and scientific knowledge of the 

 draughtsman. 



