68 



HARDWICKE'S SCIENCE-GOSSIP. 



MICROSCOPY. 



Good Microscopes. — " Why should not a micro- 

 scope be obtainable upon the same terms as a 

 pianoforte?" A large number of individuals who 

 wish to possess a good instrument are deterred by 

 the great outlay it involves at one time ; but sup- 

 posing the amount could be spread over, say twelve 

 or eighteen months, they would jump at the oppor- 

 tunity of possessing one. I should imagine that 

 some system similar to Cramer & Co.'s, Moore & 

 Co.'s, and other large pianoforte manufacturers, 

 might be adopted by opticians with great success, 

 and would eventually prove most remunerative to 

 them, as there can be no doubt that they would 

 sell a larger quantity of good and expensive instru- 

 ments, while, at the present time, students and 

 persons in the middle classes of life put up with 

 an inferior and cheaper article. If some spirited 

 optician would only pioneer the way, I am sure he 

 would be followed by many others.— C. R 0. 



Dr. J. Matthews's Turntable. — All micro- 

 scopists who use the turntable are greatly indebted 

 to Dr. J. Matthews for the improvement he has 

 carried out on the instrument formerly in use, and 

 which is described and a drawing added in the July 

 number of 1S70 of Science-Gossip. In repeating 

 his excellent principle, [ have been induced to sub- 



Fig. 44. Dr. J. Matthews's Turntable, two-thirds size. 



stitute rosewood or some hard wood in lieu of brass. 

 I find that glass slides work more pleasantly with 

 wood than with brass; there is less danger of splin- 

 tering the edges of a thin glass slide by undue pres- 

 sure, and the wood being more elastic than brass, 

 holds the glass slide equally firm, with less pressure. 

 It is of advantage to make the upper edges of the 

 jaws, where they touch the glass slide, to project a 

 little beyond the lower edges, increasing the grip of 

 the jaws on the glass slide. In the mode of wedging 

 up the wooden jaws, I adopt another form of wedge 



(also of hard wood), doing away with the slatted 

 wedge, which is rather troublesome to construct, 

 and using a circular piece of wood, on one side pro- 

 longed into an arm or lever, and secured by a brass 

 screw, the centre of rotation not coinciding with 

 the centre of the circle. This mode of wedging the 

 jaws gives great power gradually applied, with very 

 little effort, and not any chance of slipping, the jaws 

 and wedge-piece being of hard wood : the table or 

 circular plate is made as usual of brass. This mode 

 of carrying out Dr. J. Matthews's excellent principle 

 reduces the trouble and cost of construction to a 

 minimum, and where the services of a workman 

 cannot be procured, the microscopist may carry it 

 out for himself. To help explanation I have added 

 a drawing.— J. B. Spencer, 9, Kidbrooke Terrace, 

 Blackheath. 



Universal Mounting and Dissecting Micro- 

 scope.— This instrument, which has been referred 

 to in the Eebruary number of Science-Gossip as 

 "very useful and compact," has been specially 

 designed for the purpose of comprising, in a single 

 portable case, all the requisites in implements and 

 materials for the preparing and mounting of micro- 

 scopic objects, including a stock of glass strips and 

 covers, and combined with a good, simple, and com- 

 pound microscope, sufficient for ordinary require- 

 ments in collecting and examining objects either at 

 home or at the seaside, aVc. ; so as to supply the 

 means of preserving objects, whilst fresh, upon the 

 spot, that would be injured or lost if the mounting 

 were deferred until returning home. The com-, 

 pound microscope extends to a power of 200 diame- 

 ters, and the simple microscope to 20 diameters ; 

 and the whole is contained in a case of about 

 7 inches cube, and so arranged that all portions of 

 the apparatus are readily accessible for use when 

 the case is set open. This instrument has been 

 ably worked out by Messrs. Field, of Birmingham, 

 from my original design, aided by the suggestions 

 of several microscopical friends in bringing it to 

 its present very complete state ; and it is being 

 supplied by them at a very moderate cost. — W. P. 

 Marshall, Birmingham. 



British DiatomacEjE. — We are glad to see a 

 new Guide to the Genera and Species of British 

 Diatomacea?, by Dr. Donkin, illustrated by Tuffen 

 West. It is being issued in parts, but as only the 

 first part has appeared, we must not at present 

 hazard an opinion. We hope that no pains will be 

 spared to make it worthy of general acceptance as 

 the standard work on this subject. 



Objective for Gas Lantern. — Can any one 

 who has used an inch objective with an oxyhydro- 

 gen lantern recommend such a glass for the pur- 

 pose ? The majority show only the central portion 

 of the object in focus. — E. C. B. 



