112 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 16. 



Dr. Carpenter, " The varioty of tints given by a selenite film under 

 polarized light is so greatly increased by tho interposition of a rotating 

 him of mica, that two selenites — red and blue — with a mica film, are 

 found to give tho entire scries of colours obtainable from any number of 

 selenite films, cither separately or in combination with each other." * 



The apjmratus is contained in a flat box or case forming a loose stage 

 intended to be laid upon the permanent stage of the Microscope, and the 



object under examination being 

 placed upon it may be observed 

 and adjusted, or changed from 

 time to time, without disturbing 

 the Microscope or its accessories. 

 The automatic rotation is effected 

 by a specially constructed train 

 of wheelwork which, on being 

 wound up, continues in action for 

 an hour, and when set in motion 

 requires no further attention, 

 enabling the observer to watch the 

 varying effects without touching 

 the instrument. It can be used 

 with any Microscope having 

 polariscopic attachments, is self- 

 contained, and removable at 

 pleasure, and does not interfere 

 with the substage appliances. 

 The designer claims that " the beautiful and interesting phenomena 

 observable in polarizing objects under various aspects, may, with the aid 

 of this self-acting arrangement, be exhibited to a number of persons in suc- 

 cession, with an ease and a readiness not attainable by any other means." 



Rousselet's Life-box.! — Mr. C. Rousselet describes a life-box which 

 for pond-life he considers works better than any other contrivance of the 

 kind he has seen. The old life-box, which has done duty for so long, 

 has, in his opinion, the very great defect that the object placed thereon 

 is totally out of reach of the substage condenser, and, therefore, 

 incapable of being properly illuminated. 



Some years ago Mr. Swift made an improvement by fixing the glass 

 plate, on which the object is placed, nearly flush with the plate of the 

 life-box, as is shown in fig. 17. But this, however, introduced another 

 defect, " that any objects placed in the box could be examined, over the 



Fig. 17. 



whole field, only with low powers, whilst with high powers only those 

 objects placed near the centre could be reached. Now, it is very 

 frequently desirable to examine an object with a high power after it has 

 been found with a low one, and we all know how very fond living 



* Carpenter cm the Microscope, 6th ed., 18S1, pp. 132-3. 

 t Journ. Quek. Micr. Club, iii. (1887) pp. 176-7 (1 fig.)- 



