66 



HARD WICKE 'S SCIENCE - G OSSIP. 



tissues of Alliitin Po)-riim (the Leek) abound in 

 crystal prisms. To obtain them with ease, take a 

 small portion from the bulbous part of a boiled leek, 

 and press out on a slide with a little water ; examine 

 with a :}-inch, and myriads of the crystals will be 

 met with. The crystals being very minute, nothing 

 lower than a J-inch will be of much use. To mount 

 the crystal prisms use glycerine jelly or damar. Any 

 reader interested at the present time in j^lant crystals 

 should refer to Professor Gulliver's admirable paper 

 on " Raphides, Sphaeraphides, and Ciystal Prisms " 

 (Science-Gossip, 1873, p. 97). — Charles F. W, 71 

 Williams, Rcdland. 



Varnishing Cells. — I often see complaints 

 from some of your correspondents about varnishes 

 running in aud spoiling then- objects. May I be 

 allowed to suggest a plan which I have tried myself, 

 and which I find answers veiy well ? It is true it can 

 only be applied to a certain class of objects ; but 

 where it can be applied, I think it will be of some 

 use — at least to those who, like myself, do a good 

 deal of mounting. The cell (for it is only where a 

 cell is required, and one made with varnish) should 

 be held over a spirit-lamp till the varnish becomes 

 quite sticky ; the object should then be placed in it, 

 and the cover gently pressed down till it is hermeti- 

 cally sealed. In an hour or two it will be dry enough 

 to place on the turntable, when, if it is properly 

 done, there will be no fear of the varnish running in. 

 The cell should not be more than two or three days 

 old, as it gets too dry to softoi, otherwise it will 

 crack when dry. — E. W., Lewisham. 



The Pygidium.— Allow me to correct an error. I 

 stated in my paper on ihe Pygidium (p. 15), that I had 

 found a pair on the Ixodes of the tiger and Indian 

 bullock. Further examination with a higher power 

 convinces me that these are not Pygidia but spiracles. 

 — John Bravihall. 



"How TO Choose a Microscope." By a 

 Demonstrator (London : Hardwicke & Bogue). — We 

 feel personally obliged to the author of this brochure 

 for its publication. We are constantly being 

 asked to recommend tlie "best microscope,'' and 

 the "best maker." We hardly need say how invi- 

 dious this task is, and our only answer usually is 

 silence. Now, any designing purchaser may learn all 

 about the microscope and its adjuncts. In this pam- 

 phlet all the separate parts of a good microscope 

 are explained so clearly that it is impossible to mis- 

 take them ; and if it were possible, that would be 

 rendered difficult by the eighty illustrations, simple 

 but vigorous, which assist the text. The writer is 

 evidently a man of experience, and knows exactly 

 how to anticipate a student's difficulties and wants. 

 All intending to buy a microscope should first pur- 

 chase this pamphlet, and those who have one will 

 here learn how they can add to it. 



ZOOLOGY. 



A Fountain with Bell-jar Aquaria.— All 

 who have read our Editor's "Aquarium" must, I am 

 sure, have foimd much in it that was new to them, 

 and nothing but what was useful. Amongst other 

 practical suggestions, the advantage of a circulation 

 of the contained water is insisted on. Leaving out 

 the cry of trouble — a cry unworthy of consideration 

 — a great difficulty at first presented itself in arranging 

 for circulation in the inverted bell-jar form of Aqua- 

 rium. What was desired was a waste-pipe that 

 would work automatically, always keeping the water- 

 line constant ; for a siphon, when it had reduced an 

 excess of height, would empty itself and would not, 

 unless sucked, work on a fresh accession of water. 

 A hole through the bottom of the aquarium gave the 

 chance of leakage, was difficult to make, and weak- 



Fig. 59. Simple Hydrostatic 

 Arrangement for Aquarium. 



Fig. 60. Horizontal 

 Section of Ditto. 



ened the vessel. I was therefore led __to devise the 

 following simple hydrostatic arrangement. A glass 

 tube bent in an ordinary gas-flame, after the manner 

 known to all who have dabbled in chemistry, was 

 made to fonn four curves, as represented. The 

 curves A and c are made in planes, at right angles to 

 those of B and D, which are parallel, so that a hori- 

 zontal section througli xy, which represents the 

 water-line, would show the sections of five pipes, A, 

 B, c, D, and E, while MN is in each case the side of 

 the aquarium. The ends of the tube at x and y must 

 be cut off with a file on the same horizontal line, 

 which must be at the distance from M, the brim of 

 the bell-jar, at which it is desired to have the water- 

 line. Thus, with the aid of the little apparatus de- 

 scribed in the "Aquarium" a fountain can, by the 

 means just described, be adapted to an inverted bell- 

 jar, and the tube-apparatus, when once filled, can be 

 removed without emptying itself. — D. A. K. 



Vanessa Antiopa (female) I caught at Cromer 

 November 15th, 1876. This butterfly is in splendid 

 condition. — A. Savin. 



A New Species of Echidna. — The unexplored 

 area of New Guinea promises to yield many new and 

 perhaps strange species to naturalists. Announce- 

 ment has been made of a new species of monotre- 

 matous mammal which has been called Tachyglossus 

 Bruijiiii. Only two species of this animal, formerly 

 called Echidna, and which is nearly related to the 

 Ornithorhvncus, had previously been known. The 



