THe NortHERN MicRoscoPist. 
No. 8. AUGUST. 1881. 
THE MICROSCOPICAL TURNTABLE. 
ia turntable is perhaps the most important instrument in the 
hands of the preparer and mounter of objects. Originally 
devised by Mr. Shadbolt as a simple brass circular plate about three 
inches in diameter, upon the surface of which was placed a pair of 
springs for the purpose of holding down the glass slip, it has been 
the parent of several forms which have been supposed to be of 
benefit to the microscopist. In order that the slides may be easily 
centred, the table is usually engraved with a series of circles; but 
it is readily seen that such centering can only be approximate. 
In 1870, Dr. Matthews devised a turntable to accurately centre 
slides in the direction of their width, and which possessed the fur- 
ther advantage that no springs or other portions of the table rose 
above the slide, to catch the fingers or brush, during its revolutions; 
and in the next year Mr. J. B. Spencer, in a communication to 
Science Gossip, showed how this might be made in hard wood by 
the microscopist himself. 
In order to centre the slides accurately in one direction, that of 
width, Zentmayer introduced the simple device of fixing a couple 
of pins equidistant from the centre and at opposite sides of the table, 
thé slide being so arranged that it touched both of these pins. This 
centres for the width, and in length this is accomplished by a series 
of circles near the edge of the table, the operator making the 
adjustment from inspection of these. 
In Science Gossip for 1874, Mr. Bridgman described and illus- 
trated a form of turntable which, though not self-centering, enabled 
a slide to be always placed in the same position upon it, so far as 
the centre of rotation went. In 1875, Mr. C. F. Cox of New 
York, devised a self-centering turntable, which consisted of the 
circular revolving plate, in which was cut a slot in the direction of 
its diameter, and in which were moved, by means of a right-handed 
and left-handed screw, a pair of clips which gripped the opposite 
and extreme corners of the slip. It will thus be seen that so long 
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