4 Laboratory Arts 



replaces that material. Ebony is not liable to split ; it is a hard 

 and compact material, and takes a good polish when necessary, 

 though it is usually brought up to a fine finish and left so with- 

 out polishing, a coat of raw linseed oil well rubbed in, and off, 

 being all that is necessary to produce an excellent appearance. 

 It is almost impervious to water, and is not likely to break 

 down in laboratory work if used as an insulator. It is expensive, 

 and used mainly in small and delicate work. 



Box. Boxwood is used chiefly in consequence of its 

 power of retaining any shape it may be given. It may best 

 be described, perhaps, as " like beech, only more so." It is 

 of compact grain, and takes a high polish, which ensures it 

 against atmospheric action. Solids for use in mensuration, 

 scales, pulleys, and other appliances requiring absolute accu- 

 racy, in shape, alignment, etc., are made from this wood. It is 

 not, however, an easy wood to work, being very easily split ; 

 consequently it is not in great request among amateur instru- 

 ment makers. 



Sycamore and Holly are hard, white, and somewhat 

 brittle woods. 



Black Walnut is used for instrument bases and frames. 



Satin Walnut is sometimes used instead of bass wood 

 for stands. 



Oak is used for instrument bases and frames, and similar 

 purposes, being strong and hard, though of somewhat open 

 grain, brittle, and liable to split in working. Oak looks well 

 when polished or " fumed," but iron nails and screws must 

 not be used with it, as they are acted upon by the tannic acid 

 in the wood, and gradually work loose. 



The above four woods are not used to any very great 

 extent because of their intrinsic properties. They are used 

 occasionally in consequence of " figure," or because of their 

 rich appearance when polished. Oak, however, has one 

 remarkable and valuable property, viz. that when heated in 

 presence of moisture, it may be twisted into any shape, which 

 will be retained on drying and cooling. In consequence of 

 this property oak "springs" are frequently used in the 

 construction of mechanical apparatus. 



