English v. Continental Microscope Stands

Abstract

REFERRING to the interesting article on the merits of English versus Continental Microscope Stands in NATURE of December 21, 1911, I notice that whilst reasons are given on both sides for the distinctive peculiarities of the respective models, and a general suggestion is made as to how the present well-recognised types have come about, curiously enough, no reference has been made to what seems to me to be the real origin of the most important differences between the two types—I refer, of course, to the substage arrangements as a whole. Why is it that the English model provides for the exact centring, and frequently for fine adjustment focussing of the substage optical system, whilst the Continental model does not? Why is it that the Continental models, on the other hand, provide rackwork mechanism for moving the iris diaphragm of the condenser out of centre, with means for rotating this whole arrangement—a feature absent in the English model?