yVW TURE 



[May 2, 1 90 1 



The omission is probably due to the fact that the process 

 in question (Riecken's) has not been worked on a large scale 

 except during the last three or four months, though the patent 

 is three years old. Its efficacy depends essentially on securing 

 a clean mercury kathode in the form of a thin stream of mercury 

 flowing over a nearly vertical copper plate. 



The liquid containing the pulverised ore is a continually 

 agitated solution of cyanide and the anode is of iron, as the 

 electro-motive force, one and a half volts, liberates nothing more 

 corrosive than cyanogen. The particles of gold are doubtless 

 cleansed of the obstructing sulphide and tellurous films by the 

 convection currents of ionised cyanogen and also, in a more direct 

 way, by the current as it passes through each particle, making in 

 effect one side of it a kathode and the other an anode, just as is 

 seen if we suspend a piece of metal in an electrolyte between 

 the electrodes and unconnected with either. 



This simple invention may revolutionise the treatment of 

 refractory ores, yet apparently the inventor could get no hearing 

 for three years till, at his own cost, he erected apparatus on a 

 working scale in West Australia. The facts are valuable as 

 showing how great an interval separates German intelligence 

 from British engineering practice. 



Intelligence of any kind, foreign or native, must indeed have 

 been wanting when huge works, regardless of cost, were erected 

 in presence of the published electrolytic method which could 

 have been effectually tested in a single vat. 



John Hill Twigg. 



If, as your correspondent, Mr. Twigg, says, Riecken's electro- 

 lytic process has only been worked on a large scale during the 

 last three or four months, it is not unnatural that Mr. Blount 

 has omitted to describe it. In most cases Mr. Blount has 

 endeavoured to describe processes which are of proved utility, 

 and therefore it was hardly necessary to draw attention to the 

 omission. Further, the number of patents on the subject of 

 electrolytic gold refining is very large, .so that it would be 

 manifestly impossible to describe them all. Riecken's process 

 is a very neat one, and should any of the readers of Nature be 

 interested in the subject, an excellent description is to be found 

 in the " Jahrbuch der Electrochemie " (vol. v. p. 380). 



F. MOLLWO Perkin. 



Unusual Agitation of the Sea. 



On Wednesday, April 24, on going to the edge of the cliff 

 above Alum Chine, Bournemouth, at 7.50 a.m., I was struck 

 by the appearance of a succession of waves, resembling a slight 

 ground swell, reaching the shore from an otherwise calm sea, 

 there being no wind. The character of the waves was rather 

 peculiar, and I then saw that every now and then, at intervals 

 of about two or three minutes, much larger waves came in, and 

 instead of breaking abruptly, extended quietly up the sandy 

 beach to a greater height than was expected from their apparent 

 elevation. I mentioned the phenomenon on reaching the 

 house, and on the suggestion that the waves were the result of 

 a distant storm, could not see that they might be so accounted 

 for. Between 12 and i p.m. I again watched the undulations, 

 and roughly measured the length on the beach by which the 

 larger waves extended further than those of ordinary size. This 

 was about 22 feet. The larger waves were less frequent than 

 in the morning. Later in the afternoon, soon after 3 o'clock, 

 some of my family were caught by the exceptionally large un- 

 dulations, which rose surprisingly high upon the slightly sloping 

 sand. 



I have not heard whether any remarkable disturbance has 

 been recorded by the seismometer, but I see in the Daily Mail 

 and Daily Express of April 25 and 26 telegraphic reports of 

 earthqualies in Italy, Portugal and Guernsey on April 24. 



RoLLO Russell. 



RECENT DEVELOPMENTS IN ELECTRIC 



SIGNALLING. 

 T T is thirteen years since Hertz carried out the 

 ^ brilliant series of experiments which, apart from 

 their great theoretical value, had the important effect of 

 laying the foundation of modern systems of wireless tele- 

 graphy. Three years later we find the Electrician 

 making the suggestion that the discoveries of Hertz 

 NO. 1644, VOL. 64] 



might be utilised for signalling to hghtships, and five 

 years later still, in 1S96, Signor Marconi brought over to 

 England the first practical wireless telegraphic apparatus 

 and awakened public interest by the remarkably success- 

 ful experiments which he carried out on Salisbury Plain 

 and across the Bristol Channel. For a time the technical 

 and lay Press was full of wireless telegraphy ; great 

 prospects were predicted for it ; communication with 

 lightships and lighthouses was the least of the feats it 

 would accomplish ; telegraphy at sea was to become as 

 common as on land ; some even went so far as to say 

 that wires and cables of all sorts for telegraphic pur- 

 poses were to become a thing of the past. But these 

 revolutionary changes, if they are ever to be made, did 

 not come with the rapidity which many apparently ex- 

 pected. It was soon recognised that we needed to know 

 a great deal more about the subject before Hertz waves 

 were to be even a trustworthy servant to the telegraphist, 

 and even now we can scarcely call wireless telegraphy 

 much more than experiment. But we have now more 

 definite grounds for feeling sure of its ultimate success,' 

 and we can predict for it a useful future with much more 

 surety and reason than was done in the first outburst of 

 enthusiasm that followed Mr. Marconi's experiments. 



The patient and persevering experimenting of the past 

 five years has led to the gradual surmounting of many 

 of the difficulties which at first beset wireless telegraphy, 

 and Mr. Marconi, Prof. Slaby and the other pioneers 

 who have thrown themselves with vigour into its develop- 

 ment have met with a success which, if not complete, 

 is yet very promising. It is not the greatly increased 

 distance over which it has become possible to signal, an 

 increase from a few miles in 1896 to more than 200 in 

 1901, that marks the most important development that 

 has occurred. The greatest achievement is the successful 

 solution of the problem of tuning. It was early seen 

 that before wireless telegraphy could have at all an ex- 

 tended utility it would be necessary to find some means 

 of confining each message to its correct destination and 

 of preventing each receiving apparatus from responding 

 to Hertz waves sent out from any transmitter in its neigh- 

 bourhood. It seems that now almost all experimenters 

 have overcome this difificulty, at any rate to a certain 

 extent. 



The improvement in distance over which it is possible 

 to signal has been very marked. The empirical law put 

 forward by Mr. Marconi that, other things being equal, 

 the distance over which signalling would be possible 

 was proportional to the product of the heights of the 

 masts at the two ends seems to be fairly well established 

 as a working rule. But the improvements in trans- 

 mitting and receiving apparatus have been so great that 

 it is now possible to signal over much greater distances 

 with the same heights of masts than was the case in 1898. 

 For example, in 1898 Mr. Marconi was only able to cover 

 15 miles with vertical wires 120 ft. high, whereas to-day, 

 according to the recent announcement made by Prof. 

 Fleming, a distance of 200 miles from the Lizard to St. 

 Catherine's, Isle of Wight, has been signalled over with 

 masts only 160 ft. high. Mr. Marconi certainly holds 

 the record for long distance work. The example just 

 quoted refers to signalling across sea ; across land such 

 great distances have not been attained, but here again 

 we think the credit of having signalled over the greatest 

 distance must be given to Mr. Marconi, who established 

 in 1899 communication between Dovercourt and C+ielms- 

 ford, a distance of more than 40 miles. 



These long distances have been attained by Mr. 

 Marconi partly by the use of a specially constructed 

 transformer in the receiving circuit. Instead of connect- 

 ing the vertical receiving wire in series with the coherer 

 it is connected in series with the primary of this trans- 

 former, the secondary of which is in series with a con- 

 denser and the coherer. By this means the voltage of 



