1881.] 



MicEoscopicAL jour:nal. 



71 



The New ^^Acme" Lithological 

 Stand. 



[Messrs. J. W. Sidle & Co., of 

 Lancaster, Pa., have sent us a de- 

 scription of a new stand for lithologi- 

 cal work which they have designed, 

 and which will soon be placed in the 

 market ; we print it below. — Ed.] 



The "Lithological," like all our 

 stands, has our standard tubing, so that 

 the eye-pieces of one fit all the others. 

 The ordinary rotating-plate is omitted 

 and in its place a permanent rotating- 

 stage, graduated to single degrees and 

 very accurately made, is provided. 

 There will be a polarizer on a swinging- 

 arm, to allow of being turned out of the 

 way when not in use. This will be fur- 

 nished with a graduated circle, and 

 an index indicating the crossing of 

 the prisms. The mount for pol- 

 arizer has a thread in its upper 

 end to take a lens-system of extreme 

 angle. An improved centring ar- 

 rangement for the stage proper will 

 be introduced. A Klein's quartz- 

 plate mounted the same as a binocular 

 prism in the nose of the instrument 

 will be provided. This can be re- 

 moved, and the opening closed by a 

 shutter. An analyzer will also be 

 placed in the n6se, in a sliding box 

 with a stop. This also can be re- 

 moved and the opening closed by a 

 shutter. An extra analyzer, mounted 

 to slip over the eye-piece, and fur- 

 nished with a graduated disk and index 

 will be provided. Also a calc-spar plate 

 arranged to rotate between analyzer 

 and eye-lens for stauroscopic meas- 

 urements. 



The stand will be all brass, finely 

 finished and accurately adjusted. 

 Its price will not be over $90.00, 

 probably, $80.00. 



The lens-system of extreme angle 

 referred to will be the only accessory 

 to be added, to make the outfit 

 complete. 



How to Procure and Mount 

 Raphides. 



As a handsome slide of raphides is 

 always attractive, 1 give the following 

 process for obtaining and mounting 

 them : — ' 



The hanging plant known as "wan- 

 dering jew" {Tradescantia) contains 

 myriads of these needles. Place a 

 slide upon the turn-table, cut off 

 the vine or stem of the plant trans- 

 versely (somewhat obliquely), and 

 you will find the juice of the plant 

 forming a half drop on the cut end. 

 Set the table in motion without delay, 

 and place the drop on the cut end 

 upon the centre of the slide, slowly, 

 moving it outward, as the table turns, 

 so that it shall not twice pass over 

 the same spot, until you have formed 

 a scroll-like circle with the juice, of 

 about a quarter of an inch in diameter. 

 Let the slide remain fifteen or twenty 

 minutes, place a drop of fresh balsam 

 upon the centre, and place upon it a 

 half-inch cover-glass. Let the cover 

 sink down slowly until it is in contact 

 with the balsam, throughout. If not 

 level, press it gently, so that the bal- 

 sam shall fill out handsomely. Set it 

 away, but do not heat it. II will re- 

 quire some time to harden, but if in 

 haste to use it, as soon as the balsam 

 at the edge of the cover has hardened 

 somewhat, run a circle of a solution of 

 shellac in alcohol, so as to touch both 

 the edge of the cover and the slide. 

 This will hold all fast, even though 

 the balsam be still liquid within. 

 Finish this if you choose, at once, 

 paints, with tube and your slide is 

 done. Examine the slide by oblique 

 (black ground) light, or far better, if 

 you have it, by polarized light, use 

 the green, not the purplish colored, 

 " wandering jew," — you will find the 

 needles beautifully distributed, clean, 

 and looking like polished steel. The 

 needles are oxalate of lime, and are 

 beautiful with polarized light. 



S. A. Webb. 



Oswego, N. Y., March, 1881. 



