174 THE AMERICAN MONTHLY [June, 



tides wtMi' thus caujjlit in the meshes of the muslin, from which 

 they were at'terwards easily waslied by shakinj^ the cloth in a 

 >hallow dish ol" water. The hare ma>jnet wastlien moved about in 

 the disli of water, and the particles tluis collected transferred to a 

 iflass slip and mounted. A comparison witli similar particles 

 obtained from coal-asiies preseuteil scarcely any ditlerence. 



In tliis comiection it may be of interest to add that I iiave ex- 

 aniineti hail but failetl to fiml maj^netic particles, thouijh the dust 

 founil in tlie hail was considerable. Mas anybody ever tjalliered 

 such ma<jnetic spherules from hail? 



1']. H. Knkkk. 



Atchison. Kansas. A/>ri/ j^. iHgj. 



(30) Criticism of Wethered's Medical Microscopy. ( )ii 

 page 1^3 Wethered states that fresii material frozen and sectioned 

 can be used for temporary examination. Init tiiat if you want per- 

 manent mounts tiic material must be liaidcned. embedded and 

 sectioned. 



Hut I hayc many sections tliat were neyer hardened nor em- 

 l)eiide(i, which, though mounted years ago, are as good as they 

 eyer \vere. They were frozen and sectioned witii Cathcart's 

 microtome, then stained and mounted without haying been sec- 

 tioned, hardened or emliedded. Tiie beautiful sections <;f Arthur 

 Cole are made by freezing with Cathcart's microtome and without 

 embedding. 



On page 321 Wethered sa\ s that the red corpuscles are i -3200th 

 inch in diameter, but he should haye adtled that tiiey yary in size 

 both aboye and below that Hsfure. P. C. C. 



.>II( 1J()S( OPICAL APrAKATUS. 



A Cheap Microscope Illuminator. — Take any flat-wick lamp 

 with a good burner and a clear, clean chimney. Light the lamp, 

 put on the chimney, turn up the wick a little, and with a card 

 check the draught by partly covering the opening at the upper 

 end of the chimney. This will smoke the inside of the chimney 

 and make it impervious to light; or light the lamp without the 

 chimney, turn up the wick until it smokes freely, and smoke the 

 inside of the chimney until it will not show any light through the 

 blackened surface ; allow the chimney to cool, and with a piece of 

 paper remove the soot from a small part of the inside opposite 

 the brightest part of the flame. The clear spot can be placed 

 towards the edge or side of the flame as wanted. 



Providencf.. R. I. X. N. Mason. 



The Acme Lamp and Attachments. — The lamp consists of 

 a heavy base with upright, carrying a claw-shaped holder, adjust- 

 able vertically and also turning on a horizontal axis. Tliis claw- 



