June 8, iSSS.] 



SCIENTIFIC NEAVS. 



549 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents, nor can he take notice of anonymous com- 

 munications. All letters must be accompanied by the natne and 

 address of the writer, not necessarily for publication, but as a 

 guarantee of good faith. 



RE-FORESTATION OF BRITAIN. 



The suggestive article of your contributor, Mr. Mattieu 

 Williams, by no means exhausts all the advantages sure to 

 accrue from the forestation of our moorlands and wastes. 

 One of the most important is the shelter which they afford 

 against the wind, one of the greatest enemies of the British 

 farmer and gardener. Practical American authorities have 

 concluded that if about one-fourth of a region is left clothed 

 with forests, the residual three-fourths will yield more 

 abundant crops than would the whole if laid entirely bare. 



Another advantage of the woodlands is that they afford 

 ample shelter and resting-room for the small insect-eating 

 birds which are so much needed to protect our crops. 



Philibert. 



A CIRCLE PROBLEM. 



How much farther does the outer handle of one of the 

 carriages of an " Inner Circle " train travel in one journey 

 than the inner handle, the circumference of the circle being 

 13^ miles, and the handles being 9 ft. apart? 



It might be imagined by those who know that the ratio of 

 the circumference of a circle to the diameter is as 3-14159 to 

 I, or more accurately 3-14159265358979322384624338 to i, 

 that the more simple and more easily remembered ratio of 

 31 would not be accurate enough. Many persons would pro- 

 ceed thus : — Reduce the circumference to feet = 63360, 

 divide by 3-14159 to find the diameter = 20168-1 ft. Take 

 this as the distance travelled by the inner handle. The dia- 

 meter of the track of the outer handle will be 18 ft. greater, 

 or 20186-1 ft. The circumference of this circle is 63416-54 ft., 

 or 56-54 ft. longer than the inner, say, 56 ft. 6j ins. 



A little reflection shows that the circumference of the circles 

 has nothing to do with the problem, unless they are several 

 thousand miles in diameter. The difference will always be 

 the circumference of a circle 1 8 ft. in diameter. 



If the track encircles the earth, the diameter would be 

 about 25,000 miles in diameter, and the two rails being 

 parallel, the distance travelled by the handles would be the 

 same. If a telegraph line were set up alongside of this track, 

 on poles 9 ft. high, the length of the wire would be 25,000 

 miles 56 ft. 6i ins., supposing the diameter of the earth to be 

 exactly that given above. A. P. T. 



THE NEBULAR THEORY. 

 It is said that a definite star in the constellation Cygnus has 

 been seen to resolve itself into a nebula. How is this 

 phenomenon to be reconciled with the theory of Laplace? 

 Querist. 



ALKAHEST. 

 Is it possible that the " alkahest " of the old alchemists was, 

 after all, fluorine ? This substance certainly possesses the 

 most strikmg property attributed to alkahest — that of attack- 

 ing and dissolving all things. Is it possible that free fluorine 

 can have been known in times of which all record has 

 perished ? Hermes. 



FLORA AND FAUNA OF HARD AND SOFT WATERS. 

 Can you refer me to any observations as to the compara- 

 tive prevalence of aquatic plants, fishes, water-insects, etc., 

 in hard and soft waters ? My own impression is that the 

 soft water streams, when not too rapid, are decidedly the 

 richer. E. G. C. 



• *^S»^<iff5tf-» 



Remarkable Age. — The Medical Press learns the re- 

 ported death of a peasant of Moravia at the age of 142 

 years. He is said to have left a son aged 115 and a 

 grandson of 85. 



RECENT INVENTIONS. 



The following list has been compiled especially for the Scientific 

 News by Messrs. W. P. Thompson and Boult, Patent Agents, of 

 ^2Tj, High Holborn, London, W.C.; Newcastle Chambers, Angel 

 Sow, Nottingham ; Ducie Buildijigs, Bank Street, Manchester ; 

 and 6, Lord Street, Liverpool. 



SiGN.\LS. — Semaphore signals for railways have been 

 patented by Mr. H. Skerrett. The invention consists in 

 the combination -with a hollow swinging arm, having a 

 transparent front, of a light arranged exteriorly to this 

 arm and means for reflecting the light into the cavity of 

 the arm, and thence out through the transparent face of 

 the same. It also comprises the combination with two 

 movable semaphore arms of a single lamp and means 

 for illuminating both blades from the one lamp. 



Gas. — An apparatus for washing gas has been 

 been patented by Mr. J. H. Dinsmore, of Liverpool. A 

 convenient way of lightly washing the gas to remove 

 impurities is to cause it to pass below a number of in- 

 verted weirs, the edges of which are immersed to a small 

 depth in the washing liquor. The receptacles for hold- 

 ing the liquor are arranged horizontally, and may be 

 conveniently placed one above the other. A number of 

 weirs are provided for each receptacle, so that the gas is 

 subjected to repeated washings in each tray. 



Musical Instrument. — Mr. G. E. Mason has patented 

 a stringed musical instrument. The instrument is 

 trapezoidal in shape, its side being equally inclined to 

 the ends. The strings are stretched across from the 

 bottom of each side piece to the top of the opposite one, 

 thus lying in two intersecting planes. The strings 

 attached to the top of the one side are tuned to the scale 

 of C major, the opposite ones producing the sharps and 

 flats. Side sound-boards are placed between the two sets 

 of strings, and a middle sound-board under both sets. 

 A cover, open down the middle, gives access to the strings. 



Lawn-Tennis Marker. — Mr. E. Snow has patented a 

 lawn-tennis marker. It consists of a vessel for contain- 

 ing the marking material, provided with an opening at 

 the bottom through which the liquid passes on to a 

 marking wheel, by which it is conveyed to the ground 

 when the machine is wheeled along, the flow being 

 regulated by means of a valve. The valve is provided 

 with a spike to prevent the stopping up of the outlet, 

 and is normally closed by two spiral springs, being lifted 

 when required by a cord which passes over a pulley and 

 is connected with a lever handle. A scraper is fixed to 

 the bottom of the vessel. 



Aluminium. — Mr. C. A. Burghardt has patented a 

 solution for producing aluminium. The solution, from 

 which the aluminium is to be extracted, is prepared as 

 follows : — A quantity of aluminium sulphate is dissolved 

 in water, the contained aluminium being precipitated as 

 hydrated aluminium oxide by the addition of an excess 

 of ammonia solution. The aluminium thus obtained is 

 washed to free it from saline impurities, and is after- 

 wards dissolved in an excess of caustic soda, thus form- 

 ing aluminates of these metals. To the solution of alu- 

 minate is added a proportion of potassium cj'anide, and 

 the solution boiled for some time ; potassium bicarbonate 

 is then added, and the whole is boiled for twelve to six- 

 teen hours, until the solution becomes clear ; and finally, 

 to make the solution deposit the metal in a bright condi- 



