116 SELECTED NOTES FROM 



Algae. — I noticed a short time ago that boiling water changed 

 a red algse to an olive-green colour. This seemed to me to be 

 curious. I shall be glad to know the precise effect of heat on 

 Chlorophyll. H. M. J. Underhill. 



Crystallisation. — What would a mathematician say of a "cubical 

 point " capable of containing something within it ? I imagine that 



Mr. Nicholson does not hold that matter is formed of atoms. 

 The Atomic Theory beautifully explains many of the phenomena 

 of chemistry, but does not explain crystallisation. 7/^ a substance 

 did consist of atoms, the " original germ " would not be cubical. 

 We can understand that homogeneous substances, as water 

 H.O.H.^ and common salt (Sodic chloride), Na. CI., might 

 arrange themselves into symmetrical forms, but it is difficult to 

 comprehend how some of the more heterogeneous compounds, as, 

 for a familiar example. Citric acid, which is— 



( C H 2 (CO Ho) 



■j C H (CO Ho) 



( C H HO (Co Ho), can arrange themselves symmetrically unless 

 we suppose that tlie force of cohesion acts, not equally in all 

 directions, as gravitation does, but in certain directions only. 



F. J. Allen. 



Cupric Acid. — My method of making these crystal slides is — I 

 am particularly careful to have the glass-slips pei-fcctly clean and 

 free from grease, by wiping with Liq. Ammonia or Liq. Potash. 

 I then make a solution in water of the sulphate, in an equally clean 

 glass tube. I now hold the slip over my micro lamp until it is 

 almost too hot to touch, and then, with a clean glass rod, spread a 

 drop of the liquid (not too much) in the centre of the slip. When 

 it begins to steam, I gradually raise the slip from the lamp, thus 

 lessening the heat, and in a second or two the liquid will have 

 become dry, and the spirals formed. As soon as the slip has 

 cooled, I mount in Dammar, and have not yet (i8 months) noticed 

 signs of deliquescence. I do not succeed with every slide, but 

 think I get a fair average success. J. M. Williams. 



Sections of Mountain Limestone.— I must explain how it is 

 that some sections are thick. In making cuttings, only about one 

 specimen in three contains something interesting, and perhaps a 

 third of the best ones break during the process of grinding, and 

 the cracks come at the junction of shells, etc., with the crystalline 

 limestone. I therefore generally cease to " thin " when the 

 section is moderately transparent. If the rock is successfully 

 ground to extreme thinness, the nature of many of the objects 

 cannot be well seen, for the crystals of the carbonate of lime 

 attract the eye everywhere. I will endeavour to explain the dif- 



