1 84 



S CIENCE- G OS SIP. 



R. & J. Beck's xew " London " Microscope.— 

 In design of microscopes our English makers have 

 always taken the lead, but the cheaper kind of 

 Continental stand has had a large sale here, espe- 

 cially amongst our medical and other students. 

 Recognising this, Messrs. Beck, by laying down 

 new plant for displacing hand labour by machinery 

 in accordance with the practice of the day, have 

 been able to put upon the market a new stand 

 in which sound workmanship is combined with 

 cheapness. The stand follows largely the Con- 

 tinental model, but is sold at a considerably lower 

 figure than any similar Continental stand known to 

 us. The essential features are as follows : — The 

 stand is of the horse-shoe form, but the central 

 pillar is placed farther forward under the stage so 

 as to give greater facility when the microscope is 

 in a horizontal position. The base itself actually 

 rests on three inserted cork pads, which not only give 

 steadiness, but prevent any possibility of scratching 

 the table. The coarse adjustment is by spiral rack 

 and pinion, whilst the fine adjustment is of the 



New " London " Microscope. 



micrometer screw type, in which, however, a 

 pointed rod impinges upon a hardened steel plate, 

 which is itself attached to the limb of the micro- 

 scope and works upon a triangular upright rod. 

 In the larger model the milled head of the fine 

 adjustment is graduated and furnished with a fold- 

 ing pointer. The body tube is designed for use 

 with objectives corrected for the Continental length 

 of tube, but carries a draw tube capable of vari- 

 ation from 140 to 200 millimetres. The stage is 

 square and the upper surface is faced with ebonite. 

 In the larger model it measures 4x4 inches. In 

 the least expensive model a ring, of the Society 

 size, is fitted beneath the stage to carry the iris 

 diaphragm and condenser. The latter is specially 

 arranged to fit above the iris diaphragm, and the 

 arrangement is both effective and cheap. In the 

 larger models, or those fitted with more elaborate 

 sub-stage arrangements, the usual form of Abbe 

 condenser is provided for in this instrument. 



Messrs. Beck make their " London " microscope in 

 two sizes. The smaller size with sub-stage ring 

 and iris diaphragm, but without objectives, eye- 

 pieces, or condenser, costs, with mahogany case, 

 only £3 5s. 6d. The addition of a swing-out and 

 spiral focussing sub-stage increases the price to £4. 

 I he larger model, similar to the last described, 

 costs £"> 5s„ or with rack and pinion focussing sub- 

 stage £6 10s. The necessary eyepieces cost os. 

 each, the condenser in its simplest form 10s., 

 whilst the objectives are of Messrs. Beck's well- 

 known and moderately priced series. This micro- 

 scope has, like all apparatus mentioned in these 

 columns, been submitted to our personal inspection, 

 and we congratulate Messrs. Beck on its produc- 

 tion. We illustrate the smaller stand herewith. 



EXTRACTS FROM POSTAL MICROSCOPICAL 

 SOCIETY'S NOTE-BOOKS. 



[Beyond absolutely necessary editorial revision, 

 these notes are printed as written by the various 

 members, without alteration or amendment. Corre- 

 spondence on these notes will be welcomed. These 

 extracts were commenced in the September number, 

 at page 119. — Ed. Microscopy, Science-Gossip.] 



Notes by Wm. H. Burbidge. 



Development of Balanus.— On the rocks of 

 the southern and western coasts of England, when 

 the tide is out, we observe that their surface is 

 roughened up to a certain level with an innumer- 

 able multitude of brownish cones. Each appears 

 as a little castle built of strong plates that lean 

 towards each other but leave an orifice at the top. 

 Within this opening we see two or three other 

 pieces joined together in a particular manner, but 

 capable of separating. These are Barnacles, class 

 Crustacea, division Cirripedia (from cirrus, a curl, 

 and pes, a foot), order Balanidae (from balanus, an 

 acorn). Fixed and immovable as the barnacles 

 are in their adult stage, they have passed by meta- 

 morphosis through conditions of life in which they 

 were roving little creatures, swimming freely in 

 the sea. It is in these conditions that they pre- 

 sent the closest resemblance to familiar forms of 



carapa c t . 



Caudal spirje 



5rer\\al 

 -Jitarnint". 



a [}ter)r)ulc • 



labrurr). 

 Fig. 1. Naupiius stage of Balanus. 



Crustacea. Fig. 1, represents the Nauplius stage of 

 the barnacle. It has a broad carapace, a single 

 eye, two pairs of antennae, three pairs of jointed, 

 branched and well-bristled legs, and a forked tail. 

 The skin is cast twice, considerable change of 

 figure resulting. At the third moult it assumes the 

 cypris stage as represented by fig. 2, and is enclosed 

 in a bivalve shell, with the front of the head and 

 the antennae greatly developed,* the single eye 



