39 8 MANIPULATION AND PKESEEVATION OF THE MICROSCOPE 



knowledge to biological and other investigations is entered upon in 

 the subsequent chapters of the book. 



To begin his work with success if his object be genuine work 

 the student must be provided with some room, or portion of a room, 

 which he can hold sacred to his purpose. Unless special investiga- 

 tions are undertaken, it is not a large area that is required, but a 

 space commanding, if possible, a north aspect, and which can be 

 arranged to readily exclude the daylight and command complete 

 darkness. 



The first requirement will be a suitable table. 



This should be thoroughly firm, and it should be rectangular in 

 shape. A round table, if small especially, is most undesirable, as it 

 offers no support for the arms on either side of the instrument ; and 

 with prolonged work this is not only a serious, but an absolutely 

 fatal defect. 



In a rectangular table the centre may be kept clear for micro- 

 scopical work, while there are two corners at the back, one on the 

 left and the other on the right hand. The former may be used for 

 the locked case or glass shade for protecting the instrument when 

 not in use ; and when it is in use, it in no way interferes with the 

 usefulness of the table. In the same way the right-hand corner may 

 be used for the cabinet of objects which is being worked, or the 

 apparatus needful for use. 



The most important part of the table that is, the middle, from 

 front to back should be kept quite clear for the purposes of mani- 

 pulation, and a sufficient space should be kept clear on either side of 

 the instrument for resting the arms, and no loose pieces of apparatus 

 should ever be deposited within those spaces. This soon becomes a 

 habit in practice, for experience teaches sometimes painfully, by the 

 unwitting destruction of a more or less valuable appliance. 



The spaces to the right, beyond that left for the arm of the 

 operator, may be used for the work immediately in hand especially 

 for a second and simpler microscope. An instrument with only a 

 coarse adjustment and a 1-inch or a ||-inch objective w r ill suffice, or 

 a good dissecting-stand will answer every purpose. Those who do 

 much practical work will find such a plan more rapid and more 

 efficient than the cumbrous method of a rotary nose-piece, especially 

 w r here critical work has to be done. 



When work is being done in a darkened room there should be 

 on the extreme right a small lamp with a paper shade. (Special 

 shades for this purpose can be obtained from Baker, of Holborn.) 

 This light may be kept low or used for general illumination w T hen 

 required ; it is never obtrusive, and always at hand. 



A similar space on the left hand should be reserved for a small 

 round stand fitted with a flat cylindrical glass shade with a knob on 

 the top. The stand should be suitably arranged to hold two eye- 

 pieces, three objectives, one condenser, a bottle of cedar-oil (fitted 

 with a suitable pointed dipper), and a box containing the condenser- 

 stops. This is a most useful arrangement for such a table ; and it 

 need not have a diameter greater than nine inches. 



The size for the top of such a table should be 4^ x 3 feet, and as 



