10-J THE AMERICAN MONTHLY [April, 



objectionable by Dr. Dallinger. The carriage is kept in contact 

 on the rails of the stage by the spring and ivory-pointed thumb- 

 screw /?, and the pressure thereby regulated. It will be ob- 

 served that there is ample room in the opening of the sliding- 

 carriage, above the object-slides, to insert the end of the fore- 

 finger in quick focusing as recommended by Dr. Dallinger and 

 practised by many microscopists ; and also that the object-slide 

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

 This opening also permits the use of wide angle, short focus 

 or immersion substage condensers. By placing the forefinger 

 on the hold-fast «, the middle finger on the post of the spring- 

 clip c, and the thumb against the lowest corner of the sliding- 

 carriage, an object can be moved around and about the whole 

 field of view with the greatest facility and precision and perfect 

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

 in adjusting the focus as desired. Personally, I think 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 

 1-35 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 under high-power obiectives so as to allow examination 

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

 1-35 inch high, and I find this ample to securely support 

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

 power objectives. 



Report of Division of Microscopy, Agricultural Depart- 

 ment, for 1892. 



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



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 Columbian Exposition. In this 

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

 tural experiment stations of the country, and upwards of six 

 hundred 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 poisonous 

 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 



