282 MEMORANDA. 



down. I have just made another indicator, a little more 

 complicated, but "on the same principles. It is provided with 

 two grooves, cutting each other at right angles, and moving, 

 one on the top of the other, by the help of micrometric vices. 

 With this instrument, not only do I immediately refind the 

 objects, but I can measure them with a certain precision by 

 means of divided circles placed near to the racked heads of 

 the vices, opposite an index or fixed needle. Each turn of 

 these vices equalling J-th of a millimetre, the circles being 

 divided in a hundred parts, one division corresponds to ^^th 

 of a millimetre. With this new indicator I can first explore 

 in full a microscopic preparation, then refind, nearly instan- 

 taneously, the object Avhich I desire to examine afresh. To 

 conclude, I can also tell the exact dimensions of the object ; 

 I therefore call it the Heuriscopometer. Before finishing 

 this note I ought to say a word about Maltwood's Finder. 

 1 have used this instrument several times, and it has ren- 

 dered me some service. But to substitute photography 

 for the preparation, or the preparation for photography, when 

 one wishes to seek or refind objects, is trouble, and, above all, 

 a loss of time. The shortest way is always the best. — 

 MoucHET, Rochefort-sur-Mer. 



[We shall be glad to have a further account of this instru- 

 ment. — Eds.] 



Soiree of the Eoyal Microscopical Society.— In your report on 

 the Soiree of the Royal Microscoj)ical Society you mention 

 a series of fossil woods as being exhibited by me in illustra- 

 tion of a paper by Mr. Carruthers in the ' Intellectual 

 Observer.' The fossils I exhibited comprised about thirty 

 species of Graptolites (an extinct order of Hydroid Zoo^ihytes), 

 with graptolite germs, &c. ; but not a single specimen of fossil 

 wood. The papers by Mr. Carruthers in the ' Intellectual 

 Observer,' and in the ' Geological Magazine,' to which I re- 

 ferred, contain our latest and most accurate information on 

 these interesting fossil zoophytes. — John Hopkinson, 

 8, LaAvn Road, Haverstock Hill. 



Cutting Thin Glass.— A correspondent inquires how or with 

 what instrument the thin glass for mounting objects is cut I 



Blood-stains.— The ready detection of the presence of blood 

 in a medico-legal case is a matter of importance and interest, 

 and several advances have been made of late years in this 



