May 1, 1S67.] 



HARDWICKE'S SCIENCE-GOSSIP. 



115 



MICROSCOPY. 



Cuticle of Leaves.— At the last meeting of the 

 Quekett Microscopical Club, an interesting dis- 

 cussion took place on the relative advantages of 

 removing the cuticle from the leaves of plants by 

 the slow process of maceration iu pure water, or the 

 quicker one of boiling iu uitric acid. Since then I 

 have made a first and successful attempt by the 

 latter method, aud hoping it may induce others to 

 try experiments who hitherto have been deterred by 

 fancied difficulties, I now give the result. A leaf of 

 a rhododendron which had been dry for some 

 months, and a freshly gathered leaf of an azalea, 

 were put into a test tube, and covered with un- 

 diluted nitric acid of commerce — I believe about 

 1*320 specific gravity : the tube was held over a 

 spirit lamp until the acid just boiled, and the 

 contents were then thrown into a basin of cold 

 water. The cuticle of the rhododendron leaf par- 

 tially separated spontaneously ; that of the azalea 

 came off without the least difficulty The whole 

 operation did not occupy more than five minutes. 

 Undoubtedly many leaves, according to then - texture, 

 will require different strengths of acid, and longer 

 or shorter periods of boiling ; therefore, if members 

 of the club will try experiments, noting the specific 

 gravity of acid used, and, if diluted, the proportion 

 of water added, and communicate the results to each 

 other, much useful information may be obtained. — 

 W. J. B. Arnold, Fulham. 



Diatoms in Shell Eish.— Dwellers in towns 

 need not go far to obtain certain diatoms for their 

 microscopes, as a large variety is at once procurable 

 from the nearest fishmonger. This the following 

 experiments may serve to prove. During the past 

 month I purchased and brought home a quart of 

 cockles. These I opened one by one, and placed 

 what 1 supposed were the intestines (brown-looking 

 little threads, plainly visible when the animal is 

 split open with a penknife) by themselves in a 

 wine-glass. After treating these with hot acids, and 

 cleaning and washing as usual, I obtained slides 

 containing specimens of the following genera : 

 Coscinocliscus, Hyalodiscvs, Actinoptychus, Navi- 

 cula, Surirella. I then tried mussels, and got valves 

 of Cymatopleura, Bictyocha, Campylodiscus, Cocco- 

 neis, Trice ratium ; and, lastly, by cleaning the 

 washings of a few oyster-shells, obtained specimens 

 of Biddulphia, Amphitetras, Nitzschia, Pleurosigmu, 

 Statironeis, Zygoceros, &c. After a few trials, I 

 found that the most satisfactory way of getting 

 slides of the above genera was by patiently picking 

 the valves out under an erector, mounting them as 

 selected diatoms, and restricting the number to four 

 or five on a slide. This will perhaps be found a 

 tedious process, but I know of no royal road to the 

 preparation of good slides. I was told that the 



cockles were brought from Holy Island, the mussels 

 from Yarmouth, and the oysters from the west 

 coast of Scotland. — //. W. 



Rack or Binoculars.— Allow me to call the 

 attention of the various makers to an error in the 

 construction of, I believe, all binocular microscopes 

 —but one that is as easily avoided as committed. 

 The spindle of the pinions, which work the racks of 

 the draw -tubes, is, in every instrument which I have 

 seen, placed at a right-angle to the axis of the 

 principal tube. The result is (the teeth being the 

 same in both), that the left tube travels further for 

 each revolution of the pinion than the right — and 

 hence a difference of focus in the two eye-pieces. 

 Some may consider this of small importance, but I 

 maintain that a first-class instrument should be free 

 from all avoidable defects, however minute. In my 

 case, it is of considerable importance as I am un- 

 usually wide between the eyes ; and I find that 

 when the tubes of my microscope are sufficiently 

 drawn to suit my eyes, the difference in the distance 

 travelled by the two amounts nearly to -^ of an 

 inch. The obvious way of overcoming this, is to 

 place the spindle at a right-angle to a line drawn 

 from the edge of the prism to a point midway 

 between the two eye-pieces. It would thus be at 

 an equal angle to both racks, and their movement 

 would be alike. — James Vogan. 



Erector, for Binoculars. — At the March 

 meeting of the Quekett Club, a member exhibited 

 an application of the erector to Richards' Universal 

 Investigation tube, for the purpose of dissection, &c. 

 By this means an erect and binocular view of the 

 object is obtained, with little loss of light, and good 

 definition. This combination, which seems to offer 

 some advantages over the erector as usually con- 

 structed, is to be had of Mr. C. Baker, High Holborn, 

 at a less cost (including the tube) than that usually 

 charged for the erector alone. 



Spermaceti. — My attention was drawn to this 

 substance by observing the crystalline appearance 

 it gave to pomade ; and the idea suggested itself 

 that it would make a good polarizing object. I took 

 a small quantity, and proceeded with it in the same 

 manner as for fusible crystals, only that when melted 

 on the slide it should have a thin cover dropped 

 on it, otherwise the substance is too dense to allow 

 sufficient light to pass through. I think this is 

 something entirely new ; to watch the manner of 

 concretion is worthy of remark. — E. Histed. 



Turntable. — I recently felt the want of some 

 shallow cells for mounting minute crystals in pre- 

 servative solutions, and not having a turntable at 

 hand I set to work" to make one. I failed on my 

 first attempt, but was easily able to remedy its 

 faults in the second ; as it is a very simple contriv- 

 ance, and one; requiring but a small amount of 



