114 



On a Reversible Compressorium ivith Eeyolving Disk. 

 By Samuel Piper, F.R.M.S. 



(Read June lOtli, 1868.) 



FREQITE^"T iise of the ordinary live-box has made us all 

 fully aware of its attendant evils. Valuable specimens (seen 

 perhaps for the first time) are frequently crushed in the en- 

 deavour to arrest their active movements, thus showing us 

 the necessity of devising means of applying a gradual pres- 

 sure which will prevent this danger, and also be of service 

 where objects are required to be flattened when under 

 observation. 



This requisition has been completely met by the com- 

 pressorium of Messrs. Ross ; there is, however, one great 

 disadvantage attending this form, that of being non-reversi- 

 ble, which is of the utmost importance, as it is only possible 

 to examine one side or surface of the specimen, instead of all 

 its parts. 



There are two or three reversible forms at present in use, 

 all of which, however, necessitate removal from the stage of 

 the microscope, to be readjusted or turned over, and in 

 consequence, the object has again to be sought for, and if 

 small, this is not only an uncertain and tedious operation, 

 but an unnecessary tax upon the eyes and patience. 



In the arrangement I am about to submit to the Society, 

 I think I may say the advantages of both kinds are combined, 

 with far greater facilities in regard to reversibility and ease 

 of manipulation, a single motion being sufficient to show both 

 surfaces of the object almost instantaneously, without the 

 slightest disarrangement of position or of focus, and in addi- 

 tion, it is furnished with a revolving disk for the examina- 

 tion of dry objects. 



It is available for all modes of illumination, the Lieber- 

 kiihn requiring the addition of a small movable arm of 

 blackened metal carrying a central disk or spot, which can 

 be turned aside when not employed, as in Liston's dark walls. 

 It is also applicable to objectives of any depth. 



This compressoriimi consists of two circular metal frames, 

 the inner surface of each being grooved (in a similar manner 

 as in the mounting of spectacles) to receive a thin glass, 

 which is held in position by means of a thumb-screw, and in 

 event of breakage, fresh glasses may be instantly applied by 

 the most inexperienced, by simply reversing the screw and 

 dropping another into the recess. 



