CHAPTER VI 



THE MICROSCOPE STAND 



Essential In all microscopes certain characteristics are important. The 

 qaauties. q^jality of the optical portions is the essential, but the stand 

 requires to possess good adjustments and rigidity of construction 

 to enable the optical quaUties to be made full use of. Those 

 who are not competent to judge of the optical performance may 

 . be sometimes tempted to criticise small details of mechanical 

 construction which are of no importance, but certain main points 

 are worthy of consideration. 

 Base and The base and pillar of the microscope have been a subject of 



pillar. ^^jjg (jjgc^ggion among microscopists. If the instrument is 

 supported in a rigid manner, their shape and construction is not 

 of great importance. Two chief types have been made, one of 

 which has three projecting legs of varying shapes, the other 

 consists of a flat slab with a pillar fixed upon its upper side. 

 The former is generally known as the English model, and the latter 

 as the horseshoe base. It was originally introduced more or less 

 of the shape of a horseshoe, but has since been altered in its 

 outlines. Both stands rest upon the table on three toes and, 

 provided the distance apart of these toes is the same, the two 

 models are equally rigid. The horseshoe pattern relies for its 

 stability slightly more upon its weight than its size. It has the 

 advantage that it can be used rather nearer the edge of the table 

 when the microscope is in a vertical position, and that all the 

 adjustment of the substage can be more readily got at than in 

 the English model, where the side projecting legs are more or 

 less in the way of the hands. It also requires a rather smaller 

 case or bell-glass cover. Most microscopes are now made with 

 the piQar and slab form of base known as the horseshoe, or with 

 one piece that has a shape which approximates to a horseshoe 

 base and pillar combined. Far too much time has been wasted 

 in the past by arguing on the relative merits of the two forms. 

 The microscope should stand rigidly and be free from any tremor 

 in its parts. In cities or near machinery where constant vibration 

 is present it is sometimes worth while to take special measures 

 to overcome this. A slab of slate supported on a layer of cotton 

 wool an inch thick will generally damp out vibration. In a 



