136 



HARDWICKE'S SCIENCE-GOSSIT. 



believing this to be the Epistylis parasitica ? to which 

 belief I am led by its close resemblance to E. pit- 

 catilis, of which a plate may be found in Ann. $r 

 Mag. Nat. Hist., s.4, vol. ix. pi. 16, fig. L—H.E.P., 

 Long Eaton. 



A New Oblique Light Illuminator. — The 

 utility of a more or less oblique pencil of light has 

 long been recognized by those who use the higher 

 power of the microscope. The instruments con- 

 trived for obtaining this have been various, 

 and many of them very complicated and expen- 

 sive, and, so far as my owu experience goes, none 

 of them have produced a more effective oblique ray 

 than can be obtained by a mirror on a separate 

 stand, or the lamp placed at an angle with the axis 

 of the microscope. The Rev. J. Bramhall, of 

 Lynn, has called my attention to the following 

 arrangment, and asks if it is new, which, so far as I 

 am aware, it is. The subjoined diagram will enable 



Fig. 79. The Bramhall Oblique Illuminator. 



any one possessing the slightest mechanical ability 

 to manufacture one of these illuminators without 

 difficulty, a is a piece of wood 3? inches in length, 

 1J inch in breadth, and -^ of an inch thick; the 

 central perforation b is | of an inch in diameter, in 

 which is placed a silvered disk of glass or metal, c, 

 the face of which should be not less than § of an 

 inch below the upper surface of the wood, d, a ledge 

 for the slide to rest against. We will now describe 

 the method of using it, premising that a light of 

 considerable obliquity is required. The wooden 

 stage, with its mirror, is placed on the stage of the 

 microscope, and the lamp elevated some 3 or -1 

 inches above it, and a beam of light condensed upon 

 the mirror by means of a "bull's-eye." I need 

 scarcely observe that the obliquity of the reflected 

 beam depends upon the angle at which the ray 

 impinges on the mirror. The objectives with which 

 the illuminator was tested were a J of Baker's, 

 made many years ago, but a very good glass, and a 

 "Beneche No. 7," using the following objects as 

 tests •—Navicula rhomboides, N. cuspidata, N. pere- 

 grina, N. rosiellum, Synedra robusta, Nitzschia 

 sigmoidea, N. sigma (the finely-marked variety called 

 by Moller N. curvula), and Lepidocyrtis curvicollis. 

 The I resolved the transverse striae of N. rhom- 

 boides, which it had not done before ; the longitu- 

 dinal strise on N. cuspidata shown very sharp and 

 distinct, as were also the transverse striae on 



r costae of N. peregrina and S. robusta. The 

 beautiful curved striae on N. rostellum wee better 

 shown than I have ever before seen them. N. 

 sigmoidea. — The striae resolved with as much ease 

 as those on Pleurosigmaa angulatum. with a \. 

 N. sigma as difficult as N. rhomboides. The 

 " Beneche " resolved N. sigmoidea, N. rostellum, 

 N. peregrina, and S. robusta. The podura scale 

 was shown well, but not better than by a less 

 oblique ray. The mirror would probably be more 

 effective if mounted so as to slide up or down in 

 the substage tube;* but this, of course, would be 

 more expensive. It is desirable that the cover 

 should not be attached to the slide with the usual 

 black varnish, but with " dammar," or some similar 

 transparent cement. Mr. Baker, of 244, High Hol- 

 born, London, has undertaken to supply both kinds 

 of the " Bramhall oblique illuminator."—^. K. 



SOIREE OF THE ROYAL MICROSCOPICAL SoCIETJT. 



—On Eriday, April 21st, a large soiree was given in 

 the apartments of King's College, by the President 

 of the Royal Microscopical Society, to the Eellows. 

 Invitations were issued for above 1,500, including 

 the whole of the Eellows of the Royal Microscopical 

 Society, and all the distinguished foreigners now in 

 London as Commissioners from the various Foreign 

 Governments to the Exhibition of Scientific Appa- 

 ratus at South Kensington. After having been 

 received by the President (Mr. Sorby), the visitors 

 passed into the various rooms of the College, in which 

 were exhibited many objects connected with micro- 

 scopical science. Amongst the new instruments may 

 be mentioned Mr. Sorby 's arrangement for accurately 

 measuring the wave-length of the centre of absorp- 

 tion-bands in spectra ; a new form of Stephenson's 

 erecting binocular microscope, by Mr. Bevington, 

 and another by Mr. Browning, of somewhat different 

 construction. Mr. Browning also exhibited his new 

 portable microscope, which is soconstructed that the 

 body can be turned on one side, and reversed in such 

 a manner as to reduce the height to about one-half. 

 The President also exhibited a large series of speci- 

 mens illustrating his own special subjects, shown by 

 means of fifty microscopes, lent to him by four of 

 the principal makers in London (Becks, Browning, 

 Crouch, and Ross) ; and about 150 first-rate instru- 

 ments and objects were contributed by the fellows 

 of the society and other friends. These were so 

 distributed over the large apartments of the College 

 as to avoid crowding in any part. Almost every 

 branch of science to which the microscope has been 

 applied was represented. Many very interesting 

 living objects were sent direct from the Brighton 



* Further experiments prove this to be the case. Atecond 

 and smaller bull's-eje, placed as close as practicable to the 

 stage, in order to further condense the light, is desirable. 

 With sunlight the resolving power of the objective is greatly 

 increased. 



