WITH THE MICROSCOPE. I/ 



holders are packed away. The instrument is furnished with three 

 lenses, and is to be purchased at a moderate price. 



Lawsorfs Dissecting Binocular Microscope, as made by Collins, 

 pi. IX, fig. 41, though only constructed for slight magnifying power 

 is exceedingly compact and enables the observer to use both eyes. 

 It is furnished with two sets of stereoscopic lenticular prisms, dissect- 

 ing instruments, &c. It costs two guineas. 



22. Apparatus necessary for the Student. Every Student's 

 microscope should be provided with a neutral tint glass reflector for 

 drawing and measuring objects, a diaphragm, to the under part of 

 which is fitted a tube to receive an achromatic condenser or polarizing 

 apparatus : a bulVs eye condenser, one shallow eye-piece, and two powers 

 a low one, magnifying from 20 to 40 diameters, and a quarter, or a 

 four-tenths of an inch which magnifies 180 diameters, a stage micro- 

 meter, 60, a Maltivood's finder, or the plan adopted by Mr. Baker, 

 68, and an animalcule cage, 134. 



These instruments should be conveniently packed in the case 

 with the microscope. The polarizing apparatus and the achromatic 

 condenser (see page 25) are not absolutely necessary for a 

 beginner and can be purchased afterwards. The cost of the micro- 

 scope without these last instruments, but including the other 

 apparatus mentioned, in a well-made case, need not be more 

 than six pounds ; and if the microscope be mounted on a 

 cast-iron foot instead of a brass one, it may be obtained for 

 about a pound less, without its practical utility being in any way 

 impaired. 



The great number of different microscopes and the excellent 

 workmanship employed in their construction render it a difficult as 

 well as a delicate task for a teacher to recommend any special one 

 to his pupils. Although many of the instruments which I have used 

 are exceedingly good, I doubt not that there are others, which I 

 have never had the opportunity of testing, as good in every respect. 

 The names and addresses of the principal English and Foreign 

 microscope makers will be found at the end of this volume. 



OF ILLUMINATING OBJECTS. 



23. Reflected Light, Transmitted Light, and Polarised Light. 



If the internal structure as well as the external surface of an object 

 be examined in the microscope, the observer will form an idea of its 

 nature very different to that which he would have arrived at if he 



c 



