Mar. i6, 1888.] 



SCIENTIFIC NE^VS. 



261 



in the alkali waste, produced in the manufacture of soda 

 by the Leblane process, has been sufficiently successful 

 to be generally adopted. At a cost of over ;^io,ooo, 

 and after two years' hard work, the firm with which the 

 author is associated conclusively proved that, by means 

 of Messrs. Schaffner and Helbig's process, the sulphur 

 lost in the vat waste might be recovered as sulphuric 

 acid, at a cost to the alkali maker equivalent to about 

 3d. per unit of sulphur per ton of Spanish pyrites, as 

 compared with 6d. per unit then being charged to the 

 alkali trade by the Pyrites Companies. But tlie Pyrites 

 Companies at once dropped their price to 3d. per unit, 

 and so made it cheaper to throw the sulphur into the 

 waste heap than to recover it. In 1883 C. F. Claus took 

 out a patent for obtaining sulphur from sulphide of 

 ■hydrogen, mainly with a view to purify coal gas. But 

 the author thought the process might be applied to the 

 recovery of sulphur from alkali waste, and after five 

 years' hard experimental work he has perfected a process. 

 The method consists in mixing sulphuretted hydrogen, 

 obtained by passing a current of lime-kiln gases into a 

 cream of water and alkali waste, with a regulated 

 quantity of air, and sending the mixture through a layer 

 of anhydrous oxide of iron, which, by the heat generated 

 by the reaction itself, is maintained at a dull red heat, 

 the oxide of iron itself undergoing no change. Free 

 sulphur, accompanied by vapour of water, passes off, 

 the free sulphur being obtained in the fused or sublimed 

 form, according to the temperature of the kiln and of the 

 depositing chambers. The main difficulty consisted 

 in obtaining sulphuretted hydrogen free from the inert 

 nitrogen contained in the lime-kiln gases ; the details of 

 the ingenious method by which this problem was solved 

 are, however, too technical for the general reader. 



It is estimated that by this process about one hundred 

 thousand tons per annum, of sulphur could be 

 recovered, which quantity, after supplying the entire 

 home requirements, would leave from 60,000 to 70,000 

 tons available for America, into which country crude 

 brimstone is admitted free of duty. The quantity of 

 pyrites used exclusively for making soda by the Leblanc 

 process, the sulphur of which is now thrown away in the 

 waste, is estimated at about 300,000 tons a year, 

 amounting to one-half of the whole quantity imported. 



THE VICTORIA INSTITUTE. 

 On March 5th an interesting paper was read by the Rev. 

 Dr. Walker, F.L.S., F.E.S., on the distribution of the 

 butterflies of Southern Asia, the "Oriental Region" of 

 Sclater and Wallace. The lecturer gave a condensed 

 and lucid survey of the characteristics of the Lepi- 

 dopterous fauna of India and the Malay Islands, in 

 accordance with the researches of Wallace, Distant, and 

 Moore, superadding acute observations of his own. He 

 points out that the Eastern tropics possess by no means 

 such a variety of species of butterflies as does South 

 America, and is of opinion that many of the Asiatic and 

 African kinds have a wider range and distribution across 

 their continents than is the case with the same propor- 

 tion of species in the Neotropical region, which are con- 

 fined to the limits of one valley or mountain range, not 

 occurring outside or beyond. 



He resolves the splendid genus Ornithopiera into three 

 groups. Dr. Walker admits the phenomena of " mime- 

 tism " or " mimicry," but does not feel able to discuss 

 the reasons for its occurrence in the economy of nature. 



CORRESPONDENCE. 



Tke Editor does not hold himself responsible for opinions' expressed 

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

 munications . All letters must be accompanied by the name and 

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

 guarantee of good faith. 



WHAT KIND OF LEVER IS AN OAR? 



" Athletic," in his letter which appears in your issue of the 

 2nd instant, specifies the case of an oar whose inboard and 

 outboard lengths are, respectively, as 1:3. He finds it 

 difficult to reconcile the " common theory that (in the case 

 specified) the power would be | of the resistance," with "the 

 new theory that the power exerted must be three times the 

 resistance." Permit me to point out that the power exerted will 

 be the same whether we consider the oar to be a lever of the 

 first or of the second order, i.e., whether we consider the row- 

 lock as a moving fulcrum, or the blade as a stationary one, 

 and the two theories quoted are false if taken in the sense 

 which the words appear to convey. But this is a matter of 

 expression, so far as " Athletic" and I are concerned. I think 

 I see what he is driving at. 



Now, when the oar is pulled, the boat is moved, and the 

 semi-resistance R of the boat is always exactly the same as 

 the propelling force at the rowlock, and with an oar of given 

 dimensions bears a constant ratio to P, as also does S. 

 Suppose that the boat be moored, and the oar pulled. I grant 

 that the oar will now be "harder to puU" — not because the 

 fulcrum is altered in position, but because the boat's resist- 

 ance to motion cannot now be overcome, and the more 

 laborious work of forcing the water astern is now being 

 done ; power expended faster, and pressure at rowlock corre- 

 spondingly increased. 



I do not see that the "advantage" or "disadvantage" ot 

 the power affords the best criterion as to the order to which 

 a lever may belong, but the relative positions of fulcrum, 

 weight (resistance) and power should determine this. It is, 

 however, not always easy to locate the weight and the 

 power, as in the present instance, where we have the choice of 

 two positions (rowlock and blade-end) for the resistance, and 

 thus the statement that the fulcrum of a lever is that point 

 about which the moments of power and resistance are equal " 

 is useless to us because we are not decided as to where is the 

 power or theresistance,and so cannot determine their moments. 

 But it appears to be quite possible to definitely locate the 

 fulcrum, and this being done, the definite location of weight 

 and power is self-evident. I am unable to refer to the Philo- 

 sophical Magazine, but I would submit the following method 

 of locating the fulcrum from " Ausa Dynamica," p. 66 : 



" The Rev. T. K. Abbott, F.T.C.D., * * * * appeals to the 

 concise practical criterion of a fulcrum, which is, that it is the 

 point inithe lever to which, if the ' power ' be applied, no 

 effect is produced. Now, if the rower's hand were applied 

 to the oar at the rowlock no effect would be produced : but 

 if it were applied to the oar at the blade an effect ivould be 

 produced ; therefore the former place is, and the latter is not, 

 the true fulcrum of the oar for the rower sitting in the boat." 



Therefore, I would add, the oar is a lever of the first order. 

 Wm. Jno. Tennant. 



COLOURED WORDS. 



The following translation of a passage in Goethe's "Cam- 

 paign in France in 1792 " occurs in Professor Creasy's "Fifteen 

 Decisive Battles of the World." It is interesting inasmuch as 

 it tells us that the celebrated German was susceptible to 

 sensations very similar to those in the cases mentioned 

 recently in Scientific News, where different noises brought 

 different colours before the vision. Goethe, who accom- 

 panied the allied army out of curiosity, just before the battle 

 of Valmy rode forward alone in the direction of the French 

 position in quest, apparently, of "the cannon fever " of which 

 he says he "had heard so much." He arrived, he says, 

 " quite in the region where the balls were playing across me ; 

 the sound of them is curious enough, as if it were composed 

 of the humming of tops, the gurgling of water, and the whis- 

 tling of birds." He continues : — " In the midst of these 



