The Mickoscoph;. 339 



turntable with detachable hand-rests, the slip can be quickly 

 centered on the disc — a matter of some importance — and the de- 

 tachable hand-rest, which allows a higher elevation of the hand when 

 operating, will be found very convenient. An ordinary plain table 

 can be purchased from any of the various dealers for from $3 to $4. 

 The Griffith table is somewhat more expensive, costing $7.50. 



The art of cell-building is not difficult to learn, though much 

 practice is required to attain perfection in it. The procedure can 

 be described as follows : Place the turntable somewhat obliquely, 

 with the revolving disc away from the person and looking towards 

 the left, if right-handed. Center the slip on the disc and hold 

 it there with the clips or other appliances provided for the 

 purpose. Now set the disc in rapid motion. Dip a camel's hair 

 brush in the cement to be applied, (zinc- white for instance), and 

 resting the hand on the platform, touch the brush tip lightly to the 

 slip over and somewhat outside of one of the circles marked on the 

 disc. A ring of the cement will form instantly. After waiting a 

 few minutes another ring can be laid on the first one, and this can 

 be repeated until three or four light layers have been formed. The 

 cell should then be laid to harden for a day, when it will be ready 

 for use, or to be still further added to if necessary. Now for a few 

 details. The brush should be one of medium size, with a good 

 though not too delicate point. If the brush is too long or too soft 

 it will drag; if too short or too hard it will scratch. Be careful in 

 judging of the amount of cement taken. If too much is used it 

 will spread beyond the desired limit, if too little the surface of the 

 ring will be uneven. Of course these points can only be gained by 

 experience. The manner in which the brush comes in contact with 

 the slip is of considerable importance. The brush-tip should be 

 applied so that when it touches the slip the revolutions of the disc 

 will tend to pull the hairs straight away from the handle. This 

 point will be found at the spot where a line drawn at right angle 

 with the short axis of the plane of the platform would meet the 

 circle as a tangent. This line gives the position of the brush. 

 With these hints the beginner must learn for himself. The whole 

 operation is so simple in its idea that once being told what to do it 

 will not require much ingenuity to make out how to do it. 



