276 



HARDWiCKE'S SCIENCE- GOSSIP. 



Portland beds, where they are often four feet in 

 diameter. Their size thus unfitted them for rapid 

 locomotion, and it is known that they were provided 

 with a means of closing the mouth of the " body- 

 chamber" by opcrcula. The latter are occasionally 

 met with separately, and have had the distinct name 

 of Aptychm, or Trigonellites, given to them. The 

 seas of the Lias and Oolite must have literally 

 swarmed with these beautiful objects, for the Lias 

 limestone is often made up of their shells alone, and 

 the black colour is probably due to the decomposi- 

 tion of the animal matter of the soft-bodied parts. 

 The moment you strike these rich fossiliferous 

 limestones with your hammer, the blow volatilizes 

 a portion of this oil, and its sidphuretted odour 

 greets your nostrils, and tells you plainly that these 

 solid rocks are nothing but sepulchres of forgotten 

 dead ! The Lias and lower Oolite beds in England 

 are often marked by the prevalence of distinct 

 species of Ammonites, so that they serve as good 

 indices to the geological position of a stratum. 

 When cut open, the cbambers of these fossils are 

 seen partly hollow, and partly filled with crystals of 

 carbonate of lime, darkly coloured, perhaps, with 

 organic matter. When the shells are more solid, 

 they are manufactured into brooches, &c., and go 

 by the name of ''• Shell Opal." 



J. E. Taylor. 



MICROSCOPY. 



MicnoGEAruiCAL DiGTioxARY.— A Correspond- 

 ent asks — " Might not a word from you in Science- 

 Gossip bring the editors or publishers of the 

 edition of 'The Micrographical Dictionary,' now 

 in course of publication, to a sense of their negli- 

 gence in bringing out that publication so slowly 

 and irregularly ? No part has appeared since May 

 last ! Can it be that it is not intended to complete 

 it?"— /r.Z.iV. 



Bunt of Wheat as a Lens (Translation).— 

 In looking over your interesting journal, Science- 

 Gossip, which I have taken for some time through 

 my bookseller, I find, on page 92, in the volume 

 for 1S71, a very curious note from your correspou. 

 dent "P. W. M.," under the title of "Bunt of 

 Wheat as a Lens." It relates to an arrangement by 

 means of which the eye of a beetle, mounted in 

 balsam, and placed under the microscope, shows in 

 each facet the image of a small object. Without 

 stopping to consider the principal object of the 

 above note— whether the fungus Tlllclia caries 

 possesses the same optical property,— I should like 

 to ask your correspondent if he would direct mc 

 how to operate with the reticulated eye of an insect, 

 so as to obtain, under the microscope, multiplied 

 views. I do not think that an ordinary preparation 



would be sufficient. What means should I take to 

 obtain my desired object':' I venture to count'oa 

 the courtesy of the author of the note referred to'to 

 help me, and I address myself also to any other 

 microscopist who would kindly give me any 

 assistance. — A. M., Paris. 



Mounting in Balsam ORDA:\tMAR.— It is'much 

 to be regretted that directions for mountnig in soft 

 balsam or dammar should still require to be given. 

 Cuticles, insects, sections of wood, horn, transparent 

 injections, &e., can all be mounted in hard balsam 

 without the slightest difficulty. The most important 

 condition is that the balsam should be new, or, at 

 least, uncontaminated with turpentine, benzole, or 

 chloroform. Tlie plan I adopt is as follows : — Place 

 a drop (or as much balsam as is necessary) on the 

 centre of a glass slide; heat it (taking care to avoid 

 boiling the balsam) until the balsam, when cold, 

 can be scarcely indented with the nail ; take the 

 preparation out of the turpentine (draining off the 

 superfluous turpentine); place it on the centre of 

 the hardened balsam ; allow it to remain a few- 

 seconds, or until it sinks a little into the balsam : 

 now drop a minute quantity of soft balsam on it 

 and place the covering glass, slightly warmed, on 

 the soft balsam — this, if properly managed, will 

 cause it to spread over the preparation, and gene- 

 rally over the surface of the hardened balsam : now 

 place the cover and slide between a wire clip ; gently 

 warm the whole over a spirit-lamp : the heat and 

 pressure will drive out the superfluous soft and 

 hard balsam. When cool, the waste balsam may be 

 scraped off, and the slide cleaned with a little spirit 

 of wine and ammonia. There may be some very 

 exceptional specimens where the slightest amount 

 of heat would be injurious, and then, if balsam or 

 dammar is used in the soft state, the cover (a square 

 one is best) should be protected by a piece of 

 gummed black paper the width of the cover, and 

 about half an inch larger, with a hole punched in 

 tlie centre. This will prevent the cover slipping, 

 a disaster usually befalling soft balsam slides. 

 Balsam or dammar never hardens under the cover, 

 and if the cover is rubbed or pressed it invariably 

 shifts, or the medium exudes, and the slide becomes 

 a sticky abomination. My own slides may be rubbed 

 with a piece of chamois leather between the finger 

 and thumb, without receiving the slightest injury. 

 —F. lutton. 



An Eightieth OujECTivE.-At a recent meeting 

 of the Quekett Microscopical Club, held at Univer- 

 sity College, ^h\ Thomas Powell attracted consider- 

 able attention by the exhibition of an eightieth of 

 an inch object-glass made by himself. Of course, 

 under the circumstances of its being exhibited in a 

 public room, it was not possible to test this glass very 

 severely, but it appeared to perform well, defining 



