HA RD WICKE'S SCIENCE- G OS SI P. 



201 



Potamogeton fluitans, " Roth." Cambridge, A. 

 Fryer. Surrey, W. H. Beeby, Ex. Club Report, 

 18S4, p. in. Like deep-water forms of polygoni- 

 coliiis, but spikes and fruit of nutans. 



Potamogeton crassifolius, A. Fryer. Journal of 

 Botany, 1S90, p. 321. "P. Zizii x P. natans." 

 C ambridgeshire. 



Potamogeton coriaceiis (Fryer), Nolte as a var. 

 A. Fryer, Journal of Botany, 18S9, p. S. Cam- 

 bridgeshire. Like Zizii, but leaves mostly large at 

 apex. 



[To be continued.) 



METEORIC DUST? 



A N old friend, Mr. Charles Blechynden, of Alipore, 

 Hi recently gave me a small packet of the black 

 dust which gathers in the leeward corners of the 

 terraces of our houses here ; be it remembered that 

 our houses are flat-roofed, and their terraces often 

 extensive surfaces. Mr. Blechynden told me he 

 found this dust contained "meteoric iron," and that 

 by plunging a horse-shoe magnet into a handful of 

 the crude dust, minute particles clung to the edges 

 and poles of the magnet. I have since separated and 

 mounted some. The method I have adopted is the 

 following : with a camel's hair brush, I brush off the 

 fine dust which adheres to the magnet poles, and 

 collect a small quantity on a sheet of white post 

 paper. Numerous brushings result in only a very 

 small quantity. The material thus obtained from 

 the magnet poles still includes some admixture of 

 foreign matter — spores, vegetable fibres, particles of 

 feathers, broken and dried filaments of the Alga? 

 (probably an advanced stage of Protococcus coharens ?) 

 which blacken our walls within a few months of their 

 being white-washed, particles of sand and soot, etc. 

 In order to get rid of at any rate a portion of these, I 

 apply the magnet to the under surface of the paper" 

 and working it backwards and forwards, I am 

 enabled to draw out the iron particles by magnetic 

 attraction and to bring them together, towards the 

 edge of the paper, when I brush them off into a 

 drop of xylol-balsam on a slide. A cover-glass has 

 r.ow to be added, and the balsam hardened by heat 

 in the usual way. Microscopic examination shows 

 that the mount, in addition to some sand particles 

 and extraneous matters, includes a few minute 

 spherical bodies, most of them black and opaque, but 

 some clear and glass-like, and containing bubbles. 

 The opaque spheres have shiny surfaces, and look so 

 much like miniature aerolites that perhaps Mr. 

 Blechynden is correct in calling them " meteoric 

 dust." Are the transparent, bubble-bearing spheres 

 meteoric (or volcanic) glass ? 



A few measurements may be appropriate ; they 

 are taken from eight spheres passed at random 

 through the centre of the field : 2-1000"; slightly over 

 3-1000" (two) ; nearly 3-1000" ; 1-200" (this is a 



hyaline sphere with a large bubble enclosed in it) ; 



nearly 1-400" (two) ; nearly 1-250". There are 



other masses, opaque and in other respects similar in 



appearance to the spheroidal bodies, and save as to 



form, they seem to be identical in structure with the 



opaque spheres, Their contours are rounded, but 



they are irregular in outline. I have taken some 



dust from a field, and there are iron particles in it, 



but their edges are angular and jagged, and they may 



only be fragments knocked off horse-shoes by flints, 



or other hard substances. Not being myself at all 



familiar with the appearance of meteoric dust, it is 



only with some hesitation that I have chosen the title 



for this note. I enclose a little of the "dust" 



simply brushed off the poles of my magnet ; if it is 



put on a thin sheet of paper, and a magnet applied 



to the under surface of the paper, I venture to hope 



that some of the spheres of iron will be attracted out 



of the mass, and that on being mounted in balsam 



they will verify the facts above stated. Are the 



particles meteoric and is the method of obtaining 



them which I have adopted reliable ? 



W. J. Simmons. 

 Calcutta. 



ON OUR FUTURE SUPPLIES OF ENERGY. 



A GREAT question has, for a quarter of a century 

 past, been haunting the minds of all thought- 

 ful men like a ghost. The world is getting alarmed 

 at the increasing price of coal, and the fact that the 

 natural supply is more limited by every ton con- 

 sumed. As civilization progresses, energy will be 

 more required for its development, and the progress 

 of science and civilization are so strongly bound up 

 together that we cannot put them asunder. Three 

 hundred and fifty years ago, in Queen Elizabeth's 

 time, coal was hardly used at all, perhaps owing to 

 the abundance of timber which prevailed. At that 

 time the population of England did not greatly 

 exceed the present population of London and its 

 suburbs. Three centuries and a half represent a 

 microscopically small space in the evolution of the 

 human race. But within that period we have man- 

 aged to get through nearly half of the natural stock 

 of coal which Nature stored up in our British coal- 

 cellars many millions of years ago. What will be 

 the condition of those coal-cellars three centuries 

 and a half hence at our increasing multiple-propor- 

 tion ratio of consumption ? Will there be any left ? 

 If there is, will it not be too expensive to use for 

 common purposes ? No doubt other coal-fields may 

 be discovered in the interval, and, before the end of 

 the above period, will have been actively worked, 

 notably the as yet unexplored coal-fields of East 

 Anglia. 



Coal, however, merely represents the fossilised 

 energy of a by-gone geological period. Nature is still 

 charged with full abundant energy, more than we want, 



