1892.] MICROSCOPICAL JOURNAL. 195 



The stand can be furnished with a swinging substage, with or 

 without rack antl pinion movement ; and with a circuhir center- 

 ing and revolving stage, provided with a sliding carriage similar 

 to the Centennial stand ; at an additional moderate expenditure, 

 and it is well worthy of such conveniences. 



A modification of the swinging substage and mirrors can also 

 be furnished, whereby the extensible mirror-bar slides in another 

 bar which swings from a joint on the under side of the swinging- 

 bar carrying the substage. The construction allows the sub- 

 stage and mirrors to swing independently of each other, click- 

 stops indicating when either or both bars are in the optic axis of 

 the instrument ; and permits the substage to be swung aside entirely 

 and the mirrors alone to be then swung into positions for central 

 or oblique illumination, without interference from the substage. 

 The mirrors can be likewise swung aside completely to permit the 

 use of direct illumination, with or without substage apparatus. 

 These movements contribute much to convenient and rapid use, 

 as it is unnecessary to remove and afterward return the substage, 

 or mirrors, or any other part. In this instance the stage is made 

 somewJiat narrower to allow the substage to swing clear aside. 



A Microtome for 50 cents.— Dr. Hinz has described his 

 instrument in the Omaha Clinic. The main body is a tin pot 

 3 inches high by S in diameter. A bridge 3 inches wide crosses 

 the top (or open end of the can) and is soldered to the sides of 

 the pot. In its centre is an opening which is the termination of 

 the well, and around the well opening is a glass ring over which 

 the knife is to glide. The space around the well can be filled 

 with ice for freezing. Connected with the well he has a millett 

 screw four inches long and with 40 threads to the inch. One 

 revolution produces a section i-40th inch thick ; one-half revolu- 

 tion, a section i-8oth inch, etc. An amputating knife or razor 

 can be used to cut the sections. 



MICROSCOPICAL MANIPULATION. 



Examination of Cements. — -We are indebted to Mr. Wm. 

 C. Holliday, of Dunkirk, N. Y., for the following abstract of an 

 article published in a recent issue of the E7tgineering Nexvs and 

 America?! Railroad Journal . 



On pages 481 and 482 of the E^igineering News and Ameri- 

 can Railxuay yozirnal, vol. xxvi. No. 47, Nov. 21, 1891, Mr. 

 Alden H. Brown, a student of the Iowa University, gives his ob- 

 servations and conclusions concerning some of the cements used 

 by stone and brick inasons in this country. 



His conclusions are "that the relative values of any two [or 

 more or any number] cements may be determined by a micro- 

 scopic examination by observing the following rules : 



