FOR GENERAL READERS. 



Vol. II. 



FRIDAY, AUGUST 17th, iS 



No. 7. 



CONTENTS. 



Scientific Table Talk 



The Naturalist at the Sea-Side : 

 V. — Some Marine Larvse 



The Williams Single Cylinder Automa- 

 tic Cut-Off Engine (illus.) 



The Colours of Fruits and Flowers 



Sun Dials, and How to Make Them — 

 II. (illus.) 



The j. mathematical Argument Against 

 Organic Evolution 



General Notes ... 



Whirlwinds and Waterspouts — II. 

 {illus ■) 



Our Knowledge of the Bacteria 



PAGE 





PAGE 



HS 



Natural History : 







The Ratel (illus.) 



MS 



I46 



A New Evidence of Organic 







Evolution 



10 



147 



The Poison of Eels 



IS6 



I48 



Prescription for Mosquitoes 



IS6 





Miscellaneous Notes 



i.Sb 



149 



The Eath Meeting for the Advance- 







ment of Science ... 



">7 



150 



The Zoology of the Bath District— II. 



iSQ 



151 



Extinct British Butterflies.— II. 



1 bo 



'53 



Reviews : 





154 



Alkali Works Regulation Act ... 



161 









PAGE 



Model Engine-Making 







16! 



The Navigable Balloon 



in 



War 





and Peace 







161 



Geology for All ... 







162 



British Medical Association 







162 



Correspondence : 









Whence comes Man ?— 



She 



wers 





of Frogs... 







166 



Recent Inventions 







167 



Sales and Exchanges ... 







16s 



Selected Books 







16s 



Notices... 







16s 



Meteorological Returns 







168 



SCIENTIFIC TABLE TALK. 



By W. Mattieu Williams, F.R.A.S., F.C.S. 

 On page 103 of the number of this magazine for August 

 3rd is a reference to Dr. Nasmyth's results. The 

 mystery is, I think, explained by unconscious anticipa- 

 tion in my last paper, which was written before I saw 

 the paragraph or the abstract on page 114. The old 

 Welsh collier to whom I referred had learned by ex- 

 perience that he was less liable to lung and bronchial 

 troubles in winter time while working in the pit than if 

 occupied above ground. This was due to the luxurious 

 temperature below, three or four degrees above that of 

 the mean annual temperature of Flintshire, or about the 

 same as that of the Riviera in winter. This uniformity 

 of the temperature of the pits, so pleasantly cool in 

 summer, so mild and genial in winter, is doubtless the 

 cause of the comparative immunity of colliers from 

 phthisis and other lung troubles. 



It is well known that horses improve in condition 

 while working in coal pits, and I know cases (one of my 

 own among them) of ponies that after a few months in 

 the pit have materially increased in market value, and 

 have been sold accordingly. The difference is specially 

 shown in the sleek condition of the skin or hair. 



Experiments recently made in the Lake of Geneva 

 have shown that the water is much clearer in winter 

 than in summer. White discs submerged at different 

 seasons prove themselves to be visible to a depth of 

 above twenty yards in winter, but in summer disappear 

 at little more than one-fourth of that depth. Correspond- 

 ing results are obtained by comparing the depths at 

 which photographic action is obtainable at different 

 seasons. 



Why is this ? Some observations I made about thirty 

 years ago supply an answer to this question. Domestic 

 marine aquaria were then comparatively novel and 

 much in vogue. I was a victim to the mania, and wasted 

 much time upon it, trying in vain to grow the Delessevia 

 sanguined, and other beautiful sea weeds in an artificial 

 rock pool with glass sides, and thereby carry out the 

 theory that ornamental marine vegetation may under 

 such conditions supply the oxygen demanded by the 



animals. I succeeded in demonstrating the fallacy of 

 this, but discovered that another and very objectionable 

 kind of vegetation was too easily obtainable. 



I found that my tanks exposed to the sunlight of a 

 south window, where like many other such amateurs I 

 first placed them, rapidly become turbid, more like 

 green-pea soup than limpid sea-water. The same 

 occurred at about the same time in the first attempt at a 

 public marine aquarium at the Zoological Gardens. The 

 cause of this was the development of minute vegetation. 

 Fresh water aquaria similarly exposed suffered in like 

 manner, but not so severely. 



My old friend, J. Alfred Lloyd, was a fellow-sufferer 

 at the same period, but was more persevering, and 

 made the construction and management of aquaria a 

 business ; established an emporium in the Portland Road, 

 and afterwards designed and carried out very success- 

 fully the public aquaria of Hamburg, the Crystal 

 Palace, etc. 



His success mainly depended on his method of over- 

 coming the turbidity due to such vegetation, andhispracti- 

 cal abandonment of the theory of balancing animal and 

 vegetable life in artificial aquaria, which Gosse and others, 

 who merely wrote books on the subject, still maintained, 

 and apparently have not yet learned to abandon. 



Lloyd built his large aquaria underground, or in places 

 effectively shaded from direct sunlight, i.e., under con- 

 ditions which checked as much as possible this vegetation 

 that the book-theorists describe as essential. He not 

 only did this, but he further exterminated the vegetation 

 by connecting his tanks with a large reserve of water 

 kept in total darkness, or the nearest possible approach 

 to it. This is the case at the Crystal Palace. He also 

 constructed, and, if I remember rightly, patented, a dark 

 chamber adjunct to small domestic aquaria. Three 

 sides of these were slate, only the front being glass ; a 

 sloping false bottom extended upwards from front to 

 back, and contained beneath it more than half of the 

 water in such darkness as to kill all spores and micro- 

 scopic vegetation in the water, which entered the dark 

 region by convection circulation. 



The aeration of such tanks as those at the Crystal 

 Palace is effected partially by a continuous circulation 



