1890.] MlCEOSCOriCAL JOURNAL. 



"Zi 



The base and pillars may be of iron, cast in one piece and japanned. 

 This is not entirely on the score of economy. It is not essential in the 

 instrument in mind that there should be any movement of the support- 

 ing^ columns on the base. I should not try to have the foot so fixed as 

 to put either forward. The japanned surface is more durable than any 

 lacquer, and certainly better in appearance after some years of wear 

 than most brass work under similar usage. But economy in a part 

 like this is commendable, detracting nothing whatever from the best 

 service of the instrument, but, as just said, rather increasing it. 



My instrument should have a joint for inclination. One of the first 

 maxims by which a careful worker should be guided is : " Make your- 

 self comfortable." Why should I try to educate myself into awkward- 

 ness and discomfort to accommodate a faulty instrument.'^ I believe it 

 is seriously improper to train beginners to work only over a vertical 

 tube. We all know what habits arc and how easily bad ones take hold 

 upon us, especially when we are young and beginning new service. To 

 be sure, some work requires an erect instrument ; but with the joint 

 this is secured at will, and without detriment in any way beyond a 

 very slight additional expense. 



The mirrors — plane and concave — must be adjustable for focusing on 

 an arm swinging upon an axis level with the object and capable of rising 

 above the stage. I do not regard this last of the same degree of impor- 

 tance as the inclining joint, for there are other w^ays of securing the de- 

 sired illumination aside from the central beam, which is the one with 

 which all mostly work, except as specialists. Still, this American 

 "• tail-piece," as some foreign manufacturers call it, is so simple in con- 

 struction and so acceptable when needed that we cannot afford to dis- 

 pense with it. It ought to be graduated to show the angle at which it 

 is placed. We must have some fitting for substage illumination. No 

 worker with a microscope, certainly none in college classes, ought to 

 be ignorant of the use of the modern condensers. Certainly our ideal 

 stands must be constructed to permit their attachment. It very often 

 happens that a low-power objective can be used with the greatest ad- 

 vantage as a condenser ; hence for this reason our fitting ought to be 

 readily adapted to it. To get the best results the condenser must be 

 very accurately centred, which I have never been able to satisfactorily 

 accomplish v/ithout setting-screws. The screw-clamp is not sufficiently 

 manageable. 



The stage should be as low as consistent with needed room below, 

 but this last must not be trespassed upon for any consideration what- 

 ever. Four and a half inches from the table is a convenient height, and 

 probably allows all necessary room below. A half-inch low^er would 

 be preferred by some, while I should not object to a fourth or even a 

 half-inch higher, if the facilities of illumination required it. Three 

 and a half inches is sufficiently wide, and the circular form is desirable. 

 Above all things, the stage must be very firm, so strongly fashioned 

 and supported that no ordinary pressure of the hand will affect it. To 

 secure this rigidity, the method of construction, instead of great thick- 

 ness, must be appealed to. Indeed, with a strong rim the plate can be 

 quite thin, and is better so made, aside from its advantage in the use of 

 very oblique light. The stage need only be furnished with a pair of 

 delicate clips. These should be watch-spring steel or something as 



