236 



HARDWICKE'S SCIENCE-GOSSIP. 



is a great item, is next to nothing. Very thin 

 celluloid films are commonly used for instantaneous 

 coverers, and this can be employed for both, whilst 

 the thicker kind used for ordinary photography makes 

 capital slides. In fact I have some an inch square, 

 which I use in this way, mounting it temporarily in a 

 glass slide for use on the microscope. Let all 

 microscopists try it and they will not repent. 



The Use of a Substitute for Canada 

 Balsam. — The use of a substitute for Canada balsam 

 for mounting objects for microscopic use has long 

 been an object of research with me, and in fact I have 

 employed a hundred of different media and rejected 

 them one by one, until I got the one I am about to 

 describe. I use the gum thus or frankincense, which 

 is the gum or balsam of the Pinus terda, L, (loblolly 

 or old field pine) which is found in Virginia and 

 southward, common. In Florida it is very common, 

 constituting the "Pine Barrens" of that state. It 

 was described in the "Dispensatory of the United 

 States of America" sixteenth edition, 18S9, by Wood 

 and Bache, and by Wood, Remington and Sadtler, 

 as from the Pinus Australis, Mich. (Pinus palustris, 

 Mill.), and Pinus tada, Linn. It is dissolved in 

 alcohol. A saturated solution is made by adding 

 ordinary alcohol to a large quantity of the gum and 

 set by for a day or so, until it is dissolved. The clear 

 solution, which is darker than balsam, is poured off, and 

 three parts acid to one of oil of cinnamon is added to 

 nine. This is the solution that is used for mounting. 

 The gum thus is more highly refractive than Canada 

 balsam alone, and when we add to it oil of cinnamon, 

 we use liquid of the highest refractive powers that we 

 can use. To use it we dry the substance, diatoms or 

 other substance, in the cover or slide, and add with a 

 dipper (an iron wire is good) a drop or two of the 

 solution. We then warm it until the alcohol is flown 

 off and bubbles formed are driven off, and the cover 

 is pressed on the glass slide, and the whole cooled. 

 The slide is then cleaned with solution of ammonia 

 (I use a weak " Household Ammonia" ), or carbonate 

 of soda, or borax and water. A ring of asphaltum 

 or gold size can then be turned around the cover, and 

 the mounting is done. It will be found that the 

 mounting is easy as compared with Canada balsam, 

 for no turpentine is used, and as no sticky residium is 

 used, the cleaning is also easy. I think that those 

 who use it will be pleased with the results, and 

 Canada balsam mounts be sent to the limbo. 



Royal Microscopical Society. — The August 

 number of the journal of the Royal Microscopical 

 Society, besides its usual summary of current re- 

 searches relating to Zoology and Botany, Microscopy, 

 etc., contains a capital " Note on the process of 

 oviposition as observed in a species of Cattle-tick," 

 by R. S. Lewis, F.R.M.S., illustrated by eight 

 beautifully executed woodcuts. 



Mason's Projection Microscope. — Unfortun- 

 ately, in the notice of this excellent instrument, we 

 had not received the blocks for illustration, which we 



Fig. 145. — Mason's Lantern or Projection Microscope. 



Fig. 146. — Ditto, used as a Microscope only. 



intended to use so as to give our readers an idea of 

 its make and fittings. We have now the pleasure to 

 insert the illustrations, and to repeat our appreciation 

 of this Projection Microscope. 



ZOOLOGY. 



Mymarim:. — Will you give me space for a few 

 notes in connection with my short paper on " Fairy 

 Flies " in your number for August, p. 176 ? (1.) When 

 I said that the fly emerged from the egg "in the 

 handsome form you see him, without any transitions 

 through the grub and pupa stage," I meant that he 

 underwent no such changes after his emergence from 

 the butterfly's egg, for within it, and after exclusion 

 from his own proper egg, he certainly underwent 

 them. (2.) In my table the genus Litus is misplaced ; 

 the tarsi are five-jointed, and not four, as stated. 

 (3.) The term "marginal band" is puzzling. A 

 good entomologist says it means the subcostal vein, 

 and I have so described it in my table ; but I cannct 

 see that it is punctifonn in Cosmocoma, and its 

 peculiarities are in several cases difficult to make out. 

 (4.) Since my paper appeared I have seen an admir- 



