A New Reversible Com<pressorium. 871 



quarter of an inch, diameter upwards. They can either be flat- 

 tened with a hammer, or rubbed flat on both sides on a stone, 

 and fastened with ' liquid glue/ f BelFs cement/ ' marine 

 glue/ or any other cement used for fastening brass to glass. 

 The rings cost from 8d. to lOd. a gross. 



" If they are painted with Brunswick black afterwards, the 

 brass is concealed, and they present the appearance of deep 

 cement cells. The readiest plan I find is to prepare two or 

 more dozen at a time ; and as most opaque objects require a 

 dark background, my punches, purchased for cutting gutta- 

 percha, came in useful for cutting black patches. 



" I send you a plain cell, one with cement and patch, ready 

 to receive an object, and another complete. For deeper cells I 

 get a brass-turner to cut brass-tubing to the required depth. 

 The same objection as regards fungi applies to the interior of 

 ivory cells." 



A NEW REVERSIBLE COMPRESSORIUM. 



It is not long since we had occasion to notice a very excellent 

 compressorium, devised and manufactured by Mr. Ross. It was 

 worked by a single screw, afforded great facility for replacing 

 the upper thin glass, and permitted the lower and thicker one to 

 be removed, so that any object might be conveniently prepared 

 upon it, under water if necessary. This compressorium, it 

 seemed to us, might advantageously replace the live box, being 

 quite as easily used, and very superior to it whenever delicacy of 

 manipulation is required. But, notwithstanding the merits of 

 this, and of certain other forms of the compressorium as con- 

 structed by other makers, there was still room for a new one, to 

 meet requirements that are by no means uncommon in micro- 

 scopic pursuits. 



M. Quatrefage, by placing two brass pins upon the old 

 lever compressorium, enabled the instrument to be reversed, so 

 as to give a view of both sides of an object ; but there was no 

 provision to secure parallelism of pressure, and it had other im- 

 portant defects. Dr. Carpenter, in the last edition of his work 

 on the Microscope, observed that, in his opinion, nothing could 

 be more suitable to ordinary purposes than an equatic box 

 having a screw collar fitted to it in such a manner that by 

 turning this its cover may be pressed down or raised up as 

 gradually as may be desired, without any rotation of the cover 

 itself or any disturbance of the parallelism of the glasses. This 

 is the character of the new reversible compressorium contrived 

 by Mr. Slack and Mr. Richard Beck, and now manufactured by 



