422 Foot a. Strobell: A metlmd of focussing in photouiicrography. XVIII, 4. 



Practical experience with the Bausch and Lomb vertical camera x 

 led us to doubt tbe necessity of tbe heavy metal borse-sboe base 

 and iron bars to support the bellows. Tbis part of tlie outtit, wbicb 

 is more tban half the expense of the wbole, we replaced with a 

 board one foot Square and tbree - quarters of an inch thick , using 

 wooden bars screwed to tbis base to support tbe bellows. The 

 microscope can be placed on tbis wooden base, tbus utilizing 

 its weight to support the apparatus and to overcome what see- 

 med to us tbe mistake of separating tbe microscope from the ca- 

 mera base. 



The Substitution of tbis wooden camera support was first don'e 

 to test our suspicion that blurred images were due to imperfect 

 focus or a slip of tbe focus during exposure , rather tban from 

 Vibration. We were anxious to settle tbis point, as it was not 

 possible to follow the reiterated advice of the specialists , to carry 

 the wbole apparatus to the basement and set it up on brich or 

 stone pillars ! 



The pbotographical reproductions of plate III were taken with 

 what most Operators would call a reckless disregard of vibrations. 

 During tbe ten or fifteen minutes each plate was exposed , the 

 ordinary work of tbe laboratory, even Walking back and forth, was 

 not in the least interrupted. 



If pbotograpby is to be a practical aid to eytologists , tbe mo- 

 ment a preparation is found, which seems worth reproducing, it 

 should be possible to photograph it in less time tban it takes to 

 make a camera lucida sketcb. Tbis is possible with a vertical 

 camera , daylight as an Illumination (a clear day is not essential) 

 and the method of focussing we shall describe below. 



Tbe figures in plate III were taken to illustrate our method 

 of focussing, and it is to tbis method we owe any success we may 

 have achieved in our efforts to secure a faithful reproduction of our 

 preparations by photography. Its discovery was tbe result of system- 

 atic experimenting due to the realization of the inadequacy of the 

 old method for practical use. 



It is perfectly convenient to study a preparation witb tbe micro- 

 seope placed on the wooden camera base, tbus tbe camera is ready 

 for immediate use. Tben wben an interesting cytological detail is 



x ) Our first experiruents were made witb the Zeiss horizontal camera, 

 without however, the advantage of an arc light. 



