May 2, 1872] 



NATURE 



shown by the central pointer, from which pictures of the 

 beats were taken oft" on the smoked glass, forming ad- 

 mirable slides. 



Mr. R. Knight, of Wellington, who superintended the 

 making of the apparatus, devised a neat arrangement for 

 showing the lengths of resonant tubes (See Tyndall, 

 Lecture V .). It consists of a 4-ft. length of 3-inch zinc 

 tube mounted upright on a foot and nearly filled with 

 water, so as to form a cistern in which a 2-in. tube is 

 raised and lowered, answering at the proper height with 

 powerful resonance to a large tuning-fork. This appa- 

 ratus will, I expect, come into use in future as the most 

 convenient means of demonstrating the principle of 

 lengths of organ-pipes. When the instrument is used for 

 class purposes, it may be recommended that the tube be 

 graduated to quarters of an inch, so that the pupils may 

 be practised in calculating the wave-length, and thence 

 the pitch, of any tuning-fork tested by the resonant tube. 

 Further, with reference to the theory of musical pipes, it 

 may be worth while to mention that an 8-ft. length of 'l in. 

 iron gas tube serves well to produce the overtones of open 

 pipes. It is best to fit some kind of trumpet mouth-piece 

 at one end, by means of which the most elementary 

 musical scale, that of simple trumpet-music, may be 

 effectively given. 



No ready way being found of displaying Sir. C. Wheat- 

 stone's kaleidophone experiments on a large scale, they 

 were shown afterwards as table experiments. Since then, 

 however, a Chinese joss-stick has supplied the means of 

 showing to an audience the path of the end of a vibrating 

 rod. A piece of the lighted stick attached to the end of an 

 umbrella rib shows beautifully convoluted figures several 

 inches across. Any other means of attaching a bright 

 permanent spark may of course be used, and the plan 

 serves also to show the path of a point on a long 

 vibrating wire. The experiment of waving a large tuning- 

 fork to and fro while in vibration, which Mr. Sedley 

 Taylor described in Nature, vol. v. p. 321, had also 

 been noticed by us. For want of means of making 

 the result visible at a distance, it was not shown in the 

 lecture. An inch of lighted joss-stick, however, fixed 

 transversely near the end of one leg, shows well the 

 contrast between the line of light traced by waving the 

 fork in its quiescent state, and the series of dots of light 

 into which this line is resolved when the fork is waved or 

 swung while in vibration, its counteracting movements 

 bringing it to momentary rest. 



E. B. TvLOR 



ON THE SULPHUROUS IMPURITY IN COAL 

 GAS* 



THE lecturer commenced by stating the origin of the 

 sulphurous impurity in coal gas to be the iron pyrites 

 which is contained in coal, and that in the manufacture 

 of gas, when the coal is strongly heated, the sulphur of 

 the iron pyrites not only combines with hydrogen to form 

 the gaseous sulphuretted hydrogen, but also with carbon, 

 to form the very volatile liquid bisulphide of carbon. 

 Little need be said of the desirability of removing the 

 sulphur from coal gas, for in many of our large libraries, 

 such as that of the Athena-um Club, the injurious effect 

 of the sulphurous and sulphuric acids produced by the 

 combustion of gas containing sulphur, seems to be plainly 

 manifest, more especially on the leather binding of the 

 books. The gas, after leaving the retorts in which the 

 coal is heated, is cooled down, and passed through towers 

 filled with coke, over which water is kept trickling. By 

 these means a considerable proportion of the sulphur is 



•Abstract of a Lecture delivered at the Royal Institution on February 19. 

 by A. Vernon Harcourt, F.R.S. 



removed in the form of sulphide of ammonium. It was 

 shown by experiment that this washing with water could 

 only be employed to a limited extent ; as by excessive 

 " scrubbing," as it is technictUy termed, the gas is greatly 

 deteriorated as to its illuminating power. The sulphuret- 

 ted hydrogen remaining in the crude gas is easily re- 

 moved ; but the removal of the bisulphide of carbon is 

 attended with so many difliculties that up to the present 

 time no satisfactory process has been devised to effect 

 this purpose. The lecturer exhibited strikingly the two 

 methods used for the removal of the sulphuretted hydro- 

 gen, one by passing the gas over lime, and the second 

 by passing the gas over oxide of iron, and stated 

 that it is comparatively rare to find any of this 

 impurity in the gas as supplied to consumers. Up to the 

 present time no process is used for the removal of the 

 bisulphide of carbon. Mr. Harcourt has, however, found 

 that by heating a mixture of bisulphide of carbon vapour 

 and hydrogen to redness, the iormer is decomposed 

 into sulphuretted hydrogen. It will be thus seen that the 

 removal of the bisulphide of carbon from coal gas is 

 rendered possible, for by simply heating the gas to red- 

 ness the sulphur combines as before with hydrogen to 

 form sulphuretted hydrogen, which can be easily removed 

 by passing through a purifier containing oxide of iron. 

 In this way, by passing coal gas, which contained 30 

 grains of sulphur in 100 cubic feet, through a red hot tube, 

 and then through an iron purifier, the sulphur was 

 reduced to about 5 or 6 grains in 100 cubic feet. It 

 might be imagined that the passage of coal gas through 

 a red hot tube would deteriorate its quality ; but Mr. 

 Harcourt's experiments show that the contrary is the 

 case, for by passing gas of i4'9i candles rapidly through 

 a tube heated to moderate redness, the illuminating power 

 was found to be IJ'I candles, and after passing through a 

 tube heated to bright redness, its illuminating power was 

 increased to i6'66 candles. A parallel case to this is 

 seen when marsh gas is decomposed into hydrogen and 

 carbon by a series of electric sparks, the gas which is 

 obtained occupies almost twice the original volume of the 

 gas, but possesses a far greater illuminating power than 

 that of the original marsh gas, owing to the presence of a 

 small quantity of acetylene or some such body. It will 

 be seen that these experiments otfer what certainly seems 

 to be a feasible process for the great reduction of the 

 amount of sulphur contained in coal gas. 



PROPOSED OBSERVA TOR Y IN NEW 

 ZEALAND 



ON Dec. 16, 1S50, the first ship-load of emigrants, 

 under the auspices of the Canterbury Association, 

 landed at Port Lyttelton and commenced the foundation 

 of the present province of Canterbury. On Dec. 16, 

 1871, the settlement attained its twenty-first year, and it 

 was felt by a large number of gentlemen here that it 

 would be well to celebrate the majority of the province by 

 some permanent memorial. A meeting was held on that 

 day, attended by a number of the most influential resi- 

 dents ; and it was unanimously resolved to form an asso- 

 ciation for the establishment of an astronomical observa- 

 tory near Christchurch. It was remarked by several 

 speakers that this province possesses considera1:)le advan- 

 tages for such an institution. Ijetween the ocean on the 

 east and the great range of the Southern Alps on the 

 west, there stretches an expanse of unbroken plain more 

 than 100 miles in length and 50 in breadth. The re- 

 markable clearness of the atmosphere, joined to this large 

 extent of level land, renders it possible to observe a much 

 larger area of the heavens than is usually the case. The 

 meeting fully endorsed the remarks of the promoters of 



