252 THE AMERICAN MONTHLY [Sep 



too powerful, but now comes in that useful adjunct to our 

 kit — an oil lamp with a circular wick, which to me is in- 

 dispensable. Of course, one -jould use screens and ground 

 glass to cut off the excess of light given off from the lime, 

 besides stopping down the iris diaphragm at the back of 

 the substage condenser, but the image will not equal in 

 purity the one illuminated by the weaker oil lamp. And 

 then with the help of a bull's-eye there is the perfect cer- 

 tainty of getting an even ground if the slightest care be 

 taken. I would advise intending photo-micrographers to 

 study first of all the art of photography, to buy a quarter 

 or half-plate camera, and learn how to focus so as to get 

 sharp pictures, and how to get the best work out of the 

 lens they are using. Consider carefully what exposure is 

 necessary, for the power of judging can be obtained by 

 practice, and will be of the greatest service when the more 

 difficult microscopic branch is begun. 



When one can take six plates into the field, and return 

 home and develop them into six good negatives, it is more 

 than likely that the troubles of photo-micrography will 

 not weigh so heavily as to make the struggler throw the 

 whole thing up in disgust. 



The simplest way of starting is to place the microscope 

 tube, without an eyepiece, into the lens aperture of a half- 

 plate camera, making a light-tight joint with cardboard 

 and velvet, and getting illumination either by the use of 

 the mirror and daylight, or by using transmitted light 

 from an oil lamp and bull's eye. 



Much can be done in this way for practice, taking as the 

 object the foot of a fly or spider, and using an inch objec- 

 tive and a single substage condenser. 



After getting some successful photo-micrographs and 

 feeling certain that the interest aroused is not transient, 

 buy a proper apparatus with the best objectives you can 

 afford. Messrs. Watson & Son, High Holborn, make two 

 or three kinds of photo-micrographic cameras which can 



