EECEEATIVE SCIENCE. 



175 



form assumed by plants and animals. A cer- 

 tain crystal will produce crystals of a like 

 kind, but not of anotlier, just as the seed of 

 one plant produces its kind, but no other ; 

 thus : — Dissolve three ounces of sulphate of 

 soda (Glauber salts) and two ounces of nitrate 

 of potash (saltpetre) in five ounces of boiling- 

 hot water ; divide the solution into two 

 bottles ; in one place a small crystal 'of salt- 

 petre, and in the other a crystal of Glauber 

 salts ; allow them to cool slowly, when it will 

 be found that saltpetre only will crystallize in 

 one bottle and Glauber salts in the other, 

 growing up from the crystal seed that was 

 put in. Crystallization is the first link of the 

 chain that unites man with the " dust of the 

 earth." The slower crystals are formed, the 

 more beautiful and regular they appear ; but 

 as it is interesting to see them form quickly, 

 though not of good shape, we give the follow- 



ing experiment, by which a liquid is made to 

 become almost solid in an instant. Take half 

 a pound of Glauber salt, crush it to powder, 

 and pour upon it half a pint of boiling water. 

 As soon as the salt is dissolved, pour ofi" the 

 clear hot liquor into a warm glass-tumbler, 

 and set it in an undisturbed place. 'Now, as 

 quickly as you can, put a table-spoonful of 

 sweet oil on the surface of the solution, 

 and let it stand till quite cold. In this 

 state it will remain liquid, but if touched 

 with a piece of wood, or if anything 

 be dropped into the glass, the whole will 

 instantaneously crystallize. If a bottle 

 be quite filled with the hot solution, 

 and corked up while hot, it will remain 

 liquid when it becomes cold, but when the 

 cork is drawn, crystals will be rapidly 

 formed. 



Septimxts Piesse. 



CLOCK- WOEK CHEOMATYPES. 



I HAVE invented an instrument analogous 

 to the Colour-Top, giving steady revolu- 

 tion, easily commanded, efiecting a perfect 

 blending of the coloured radials, and, at the 

 sametime, affording a proper focus, or point 

 of view, from which rightly to discern the 

 curious and pleasing effects of the groups of 

 tints. 



There is no particular rate of speed neces- 

 sary for the elimination of all effects, for they 

 become apparent as soon as the colours are 

 made to revolve; some are produced by slow 

 motion, while others require rapid revolution 

 to discover their beauties. It will, therefore, 

 be quickly perceived that the top which can 

 only be used at a high rate of speed is limited 

 in its application, and, by its rapidity, over- 

 shoots many combinations, which are thus en- 

 tirely lost. It has also the quality of being 

 erratic : it may, unless carefully watched, 



find its way to the floor, rotating upon your 

 best corn en route, or it may pirouette amongst 

 the gentle shepherds and shepherdesses we 

 so carefully preserve under French-shades, 

 to their disadvantage ; and for evening use 

 it is not very applicable. 



My simple little machine entirely reme- 

 dies these — various rates of speed are obtain- 

 able at wUl, the string " winding-up act " is 

 obviated, many original and beautiful effects 

 are produced, while a proper light may be 

 chosen ; and, as it may be used by artificial 

 light, our friends have the opportunity of 

 viewing the beautiful effects during the long 

 evenings. 



Upon a polished oak stand I have 

 mounted a few wheels of an aged brass time- 

 piece, the arrangement of which will be rea- 

 dily understood from the diagrams (Figs. 1 

 and 2). 



