The Microscope. 177 



and Co., has proposed a form made of brass and applied beneath 

 the cap of the e3^e-piece. Dr R. H. Ward, of Troy, N. Y., has 

 also devised a form which is light in weight, being made of hard 

 rubber, and easily used, as it is not applied to the eye-piece, but 

 to the top of the body tube, so that the ocular may be changed 

 without removing the eye-shade. By simply turning it over it 

 may be used before either eye. Messrs Bausch and Lomb manu- 

 facture it. Both of these are useful and commendable, but Dr 

 L. B. Hall of Philadelphia, has described another device for this 

 purpose that may be made at home. 



Dr Hall's eye-shade consists of a small opaque disk supported 

 by a wire extending from its outer edge downward to a point on 

 the tube low enough to be out of the way of the nose, then bent 

 upward parallel with the tube, but not touching it, and attached 

 to a ring near the top. His own was made of No. 18 brass wire 

 about twenty inches long, with a loop about If inches in diame- 

 ter at one end and covered with black paper to form the disk. 

 The other end is made into a ring to fit the body tube, and the 

 intermediate wire is bent as described. The ring about the body 

 may be covered with chamois skin if desired, to protect the 

 lacquer. 



Having placed the microscope in position, with the object in 

 place and the field well illuminated, the microscopist has only 

 to sit at his ease and pursue his investigations. How he shall 

 study the object depends upon that object and upon the idiosyn- 

 crasy of the microscopist. It cannot be taught in these chapters 

 which treat the subject only in a general way. But, the investi- 

 gation finished, the instrument must be returned to the case and 

 cared for carefully. No machine, and no instrument of any 

 kind, will take care of itself. The owner must attend to its wants 

 and needs, or neglecting these, he will pay the penalty in the 

 instrument's decreased usefulness and service. 



To return the microscope to the case demands movements the 

 reverse of those used to take it out. The body is racked up, the 

 objective unscrewed, taking care not to drop it or to strike it 

 against any hard substance, and it is then gently replaced in its 

 brass box and the lid screwed on. The slide is taken from the 

 stage, and if permanently mounted, is returned to its proper 

 cabinet ; the mirror is returned at right angles to the optic axis 

 of the instrument; the eye-piece is removed and deposited in 



