10-j rilK AMKKICAN MONTHLY jApiil, 



ohjoclionahlc l>v Dr. Dalliiii^cr. TIk" c;ini:iL;;c is kept in contact 

 t)n the rails ot' tlic !>ta«;c l>v the sprinj; ami ivorv-poiiitcil tluinib- 

 screw P. and tlu" pressure thereby rej^ulatetl. It will he oh- 

 serve«l that there is ample room in the openint; of" the sliiling- 

 carria<;e. above the object-sli«les, to insert the end of the fore- 

 lin};er in tpiick fociisinj; as recommentled by Dr. Dallinger and 

 practised b\ many microscopists : and also that the object-slide 

 is not clipped in a rijjiil position, but can be when desired. 

 This (»pening also permits the use of wide angle, short focus 

 or immersion substage condensers. By placing the forefinger 

 (»n the holil-fast </. the middle finger on the post of the spring- 

 clip f". anil the thumb against the lowest corner of the sliding- 

 carriage. an object can be nn)ved around and about the whole 

 tieltl of view with the greatest facility and precision and perfect 

 control, while the other hand is constantly used at the same time 

 in atljusting the focus as desired. Personally, I thiidv such a 

 carriage should be as light as possible consistent with sufficient 

 rigidity in construction. My own weighs only a little over one 

 ounce; the brass part, supporting the object-slides C\ being 

 \-z^ inch thick, and that holding the broad glass rail A double 

 that thickness. The ledge against which the object-slides lie 

 should, I think, be lower than their average thickness, to permit 

 passing imder high-power objectives so as to allow examination 

 even to the extreme edges. The ledge of my own carriage is 

 I-2S inch high, and I find this ample to securely support 

 ordinary object-slides, and low enough to pass under the highest 

 power (objectives. 



H<>|)<»rt of l)ivisi(»ii of .Microscopy, Ac^ricultiiral Dcpart- 

 iiKMif. for 1S1)2. 



[Extracted from the Report of the Secretary of Agriculture. J 



During the past year this division has been largely engaged in 

 collecting specimens of the edible and poisonous mushrooms of 

 the United States and Territories, which are intended for exhibi- 

 tion, collectively, at the World's Columloian Exposition. \u this 

 work the division has had the cordial assistance of the agricul- 

 tural experiment stations of the country, and upwards of six 

 liundretl models have been made of individual specimens in this 

 collection. The models will be colored from nature, and 

 grouped and classed according to their edible or poi-sonous 

 character. The groups, as a whole, will illustrate in miniature 

 a forest scene, and indirectly will show some of the permanent 

 causes of forest decay. 



In consequence of the increased demand by the public for 

 information relating to the cultivation of edible mushrooms, this 

 subject has received continued attention, and new illustrations 



