100 



HARDWICKE'S SCIENCE-GOSSIP. 



leaves become crisp, which rarely occurs, a few 

 minutes' residence in water renders them pliable. 



In making sections of leaves, longitudinal cuts of 

 midribs may be made, or vertico-transverse cuts 

 through the midrib, including one-third of an inch 

 of leaf on either side, or through several veins; 

 leaves and small stems held against a piece of potato 

 or turnip that has been hardened in alcohol, may be 

 cut with a razor flat on the side, which is inferior 

 when the back is held towards you. Alcohol 

 should be poured over the object and razor while 

 cutting. Large] stems are better cut in a section- 

 machine, using paraffine as an imbedding agent. 

 The object should be flooded with alcohol while 

 cutting, and the paraffine should be trimmed to a 

 cone-shape around it after every two or three cuts. 



A knife I use with my section-cutter acts so 

 satisfactorily upon both animal and vegetable 

 tissues that I will describe it. It weighs 7h ounces 

 (avoirdupois). The handle is stout, and is 4$ inches 

 long by Ik inches wide, the blade is 7h inches long, 

 the back being k inch thick. [The inferior side, 

 holding the back towards you, was first ground fiat 

 and afterwards slightly concave from back to edge. 

 A similar knife I find is figured in Mr. Rutherford's 

 " Outlines of Practical Histology." 



A list of some of the vegetable objects I have 

 found most interesting may be acceptable to some 

 of the readers of Science-Gossip. 



Leaves.— Drdsera rotundifolia, Dionea muscipula, 

 Hepatica triloba, Oxalis stricta, flava, hirsuta, and 

 Bowiei ; Deutzia gracilis, cruenta, and Portunii ; 

 Tradescantia zebrina, Eucalyptus globulus, Buchu 

 aerratifolia, Cassia acutifolia, Rhus Toxicodendron, 

 Adiantum cuneatum and pedatum, Pteris serru- 

 lata, Elae agnus. 



Sections of Stems and Midribs. — Picus elastica. 

 Strelftzia Regina, Althaea rosea, Asclepias cornuta, 

 Rubus villbsus, Impatiens Balsaminia, Pteris aqui- 

 lina and serrulata, Paulownia imperialis. 



Sections of Stems.— Aspidium Pilix mas, Ricinus 

 communis, Musa sapientium, Euphorbia splendens, 

 Datura stramonium, Dracaena Braziliensis, Ailan- 

 thus. 



Baltimore, U.S.A. 



THE "SEAR LAMP." 



[" HAVE been giving my attention of late to the 

 - 1 - subject of illumination for the microscope, and 

 having used all the various forms, from the date of 

 Mr. Pilsisetur's lamp of 1850 down to the present 

 time, I came to the conclusion that there was yet 

 something needed to render microscopical illumina- 

 tion as perfect as the use of pctroline or paraffin will 

 allow. 



Having mentioned the subject in the course of a 

 conversation with Mr. Silber, the inventor of the 



now well-known " Silber Light," that gentleman at 

 once entered into the matter, and has constructed 

 for me a microscope lamp in the form which I have 

 illustrated in the following sketch, and which I will 

 at once proceed to describe. 



,^w.;:i,.. 



Ull 



Fig. 48. Sketch and general details of the "Sear Lamp" 

 for the Microscope. 



A is a solid brass foot, only half an inch in 

 thickness, circular, and 7 inches in diameter. B, 

 the oil-holder, which holds about sixteen hours' 

 supply, and is of the same form as A, the stand ; but 

 as its total depth is only about 1 inch, the burner, 



D, can by this form of lamp be brought down several 

 inches closer to the table, or rather closer to the 

 plano-concave reflector of a microscope, than by any 

 other form of lamp of equal power ; and as light 

 increases as the square of the distance, the increase 

 of illuminative power obtained by this mechanical 

 arrangement is important. C is a tubulated aper- 

 ture forming a small funnel for the purpose of 

 replenishing the lamp, secured by a butterfly nut, 

 and thus obviating the disagreeable necessity for 

 extinguishing the lamp and screwing off the burner, 

 in order to supply fresh oil. D, the Silber burner. 



E, a strong cylindrical brass stem, upon which both 

 the lamp-body, B, and the accessories, P and G, 

 slide ; the latter being clamped at any convenient 

 height by their binding screws, and the oil-holder, 

 B, by the long radial screw shown in the sketch, and 

 which for greater facility of manipulation has been 

 extended to the periphery of the cylindrical oil- 

 vessel. P is a large plano-convex condenser, 

 which, being mounted on a jointed telescopic arm, 

 can be placed at any angle, and close to or more 

 distant from the flame. As I write, a friend of mine 

 is reading his " Gossip " at 18 feet distance from 

 the lamp, the condenser being interposed close to 

 the flame ; but this is only mentioned to show its 

 power, and not its superiority as a reading-lamp. 

 G, a slide bearing two rings ; the lesser is 2f in. 



