Junu 29, 1888.] 



SCIENTIFIC NE\VS. 



621 



animal magnetism, electrobiology, statuvolism and the 

 like are strictly identical or not. All are dangerous if 

 indiscreetly or malevolently used. Very lately the 

 Italian Government, acting under the advice of Professors 

 Combroso and Tommasi, interdicted the exhibitions which 

 were being given by one Donato, a " magnetiser," who 

 had made upwards of forty persons ill in Milan and in 

 Turin. The governments of Austria and Germany had 

 some time previously forbidden one Hansen to ply this 

 dangerous calling within their borders. In our "free" 

 country the quack, of all types, has free course and is 

 glorified, the law of libel being his sword and shield. 

 But without fear of legal proceedings we may at least 

 warn every person not to allow himself — or still more 

 herself — to be " magnetised," save under competent 

 medical advice. 



CORRESPONDENCE, 



The Editor does not hold hitnself responsible for opinions expressed 

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

 tnunications . All letters must be accompanied by the name and 

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

 guarantee of good faith. 



A CIRCLE PROBLEM. 

 I regret that several slips appear in the letter on p. 549, 

 under this title, but whether they are due to the printer, or 

 to my own carelessness, or to the wilful obstinacy of my 

 type-writer I cannot tell. It is well known that most type- 

 writers spell abominably, but mine occasionally makes state- 

 ments which astonish me The length of the circumference 



in feet should be 71,286, and this may be taken as the dis- 

 tance travelled by ths inner handle (not the diameter, as a 

 transposition of sentences suggests). On a practically flat 

 surface the difference in length of the circumferences will be 

 as I have stated, but we cannot get a flat surface on the earth 

 if we take circles of several thousand miles in diameter, and 

 when the surface ceases to be flat, this solution of the 

 problem ceases to be true. The diameter of the earth in 

 round figures is 8,000 miles, or, as Whittaker's Almanack 

 gives, 7 '896, or, for those who don't like round figures, 

 Chambers' table give 20,923,600 ft. as the equatorial diame- 



ter. Another 26 miles would give a circumference of almost 

 exactly 25,000 miles. 



Having corrected the blunders, allow me to give an ex- 

 planation of the apparent parado.x. Fig. i represents a 

 circle 18 ft. in diameter, the circumference will be about 

 56-54 ft. The track of the inner handle in this case would be 

 zero, the outer handle simply revolving round it. In fig. 2 

 the track of the outer circle is made up of four straight parts, 

 and of four quarters of a circle, the radius being as before, 

 9 ft. It is evident that the outer handle does not travel 

 farther than the inner while on the straight portion, but on the 

 curves it travels farther by a distance equal to the circumfer- 

 ence of the circle in fig. i, viz., 56-54 ft. Again, in fig. 3, where 

 there are 6-6ths of a circle, by the same reasoning the diifer- 

 ence in the lengths of the outer and of the inner track will still 

 be 56-54 ft. Now the inner circle of fig. 4 may be considered 

 as a polygon of an indefinitely great number of sides, 

 and the outer circle, as consisting of indefinitely short straight 

 parts and curved parts, the difference will still be the same. 

 If the track is in the shape of fig. 5, or any other irregular 

 figure, the difference will still be the same. A. P. T. 



THUNDERSTORMS AND LIGHTNING ACCIDENTS. 



As the season of thunderstorms and lightning accidents is now 

 approaching, I hope you will kindly allow me to make known 

 through your columns the fact that, in the interest of science, 

 the Institute of Medical Electricity is very desirous of obtain- 

 ing authentic information concerning lightning accidents, 

 whether fatal or otherwise. I should therefore esteem it 

 a favour if some of the many friends of humanity among your 

 readers will assist us to investigate these phenomena by 

 sending me such particulars of accidents of this nature as 

 they may have personal or reliable knowledge of as soon 

 after they occur as possible. Of course, electrical and 

 physiological details are what we most require, but reliable 

 general information is often very valuable, and will be grate- 

 fully received." — H. :Jewman Lawrence, A.S.T.E. and E, 

 24, Regent Street. 



"A PLEA FOR THE SPARROWS." 

 A paragraph in the Scientific News (p. 568) ascribes the 

 plague of insects in Kent to the " scarcity in sparrows." 

 Now, without entering upon the very questionable character 

 of the sparrow as a vermin-destroyer, I must beg to point 

 out, in reply, that the plague of caterpillars and grubs is 

 severely felt in parts where there has assuredly been the 

 destruction of sparrows, to wit, Epping Forest and its sur- 

 roundings. It is perfectly possible that the methods taken 

 for thinning the sparrows have destroyed or banished the 

 useful birds. Sigma. 



The Value of Scientific Education. — 'We find in a 

 contemporary an advertisement for a " chemical assis- 

 tant to science master in public school, able also to teach 

 swimmingP What remuneration will be offered for this 

 double qualification we are unable to say, but we fear the 

 sum will be very trifling. 



Congress of the French Association for the Ad- 

 vancement OF Science. — This congress has hitherto 

 received very little notice in the scientific press. Le 

 Temps oi A-pxil 21st devotes more than a column to the 

 account of an excursion made on April 3rd to some Arab 

 villages near Oran, but of the papers read we find 

 nothing. How is this ? 



Effects of Severe Weather. — The experience of 

 the past seven months goes far to show that cold weather 

 has exceedingly little efficacy in checking epidemics. 

 The old faith in its power of destroying insects has long 

 been found to be baseless, since the ova of many of the 

 most noxious species bear a temperature of 22° F. below 

 zero without injury. 



