1886.] 



MICROSCOPICAL JOUENAL. 



that as the screen or sensitive plate, 

 upon which the image formed by an 

 objective is received, is moved further 

 away, the objective must be brought 

 nearer to the object in focussing. 



Fig. 2. — Walmsley's Photo-Micrographic and Copying Camera. 



The objective, however, being made 

 for use with an ocuhar, it will readily 

 be seen that it can only be working 

 at its ])est when the rays of light pass 

 through it in the same manner as they 

 do when viewing an object with the 

 ocular. Oln'iously, therefore, when 

 the objective approaches nearer the 

 object, to form an image on the dis- 



changes in the length of body-tube. 

 To correct, or rather to obviate, any 

 defects in the image due to this 

 cause. Dr. Woodward, after numer- 

 ous experiments, succeeded in using 

 an amplifier in such 

 a manner that the ob- 

 jective, being prop- 

 erlv focussed upon 

 the object with the 

 ocular in the usual 

 manner, remained in 

 that position, the im- 

 age being focussed 

 on the screen by mov- 

 ing the amplifier 

 only. In this way 

 the finest photo-mi- 

 crographs yet made 

 have been produced. 

 We have omitted all reference to 

 the method of working without a 

 camera in a dark-room, so much fa- 

 vored in the past by various workers, 

 for the reason that it involves con- 

 siderable expense in fitting up, and 

 the plan does not ofter any advan- 

 tages, so far as we can discover. 

 It should not be inferred from any- 



FiG. 3. — Walmsley's Photo-Micrographic Equipment. 



tant screen, the lens must be working 

 at a disadvantage. The importance 

 of this fact may be more readilv ap- 

 prehended when one considers how 

 sensitive some objectives are to slight 



thing we have written that large 

 plates are required for scientific pur- 

 poses. On the contrar}', a 4 X 5 plate 

 serves every purpose, and for the 

 amateur it is far better than larger 



