Organic Remains, Crystals } and Artificial Objects. 99 



while the rest is kept back ; the few loose grains are 

 dropped on to the solution, and the lovely crystalliza- 

 tion at once commences; but it requires a little 

 practice to show it with certainty, and at the best 

 moment. 



If a simple salt has to be shown by transmitted 

 light, the microscope's mirror must be arranged ac- 

 cordingly, and then, the solution being placed on the 

 slide, must be watched, especially at its upper part, 

 which will appear in the microscope to be the lower ; 

 the film being thinnest there, the crystallization will 

 probably commence in that part. Some salts require 

 the slide to be more or less warmed, and a wax night- 

 light always occurs to my mind as the very tidiest and 

 simplest way of doing this. A few trials will show 

 whether warming is advisable or not. The process of 

 crystallization can be shown over and over again by 

 wiping away the solution each time, and cleaning the 

 slides ; and considering the powerful destructive ten- 

 dencies of some salts, it might be well to end the 

 performance by wiping the colour-tray itself, lest its 

 Gontents might get on clothes and do mischief. It 

 may chance that some of the crystals will have been 

 more than usually beautiful, and the experimentor may 

 wish to preserve them; this can generally be effected 

 by dropping Canada balsam over them, or a little oil, 

 after which they can be covered with thin glass, and 

 mounted in the ordinary way. 



We are presently to imagine ourselves enjoying a 

 summer entertainment, observing living creatures in 

 the animalcule cage, in the " ample field " of a watch- 



