ADVANCEMENT OE SCIENCE. 



115 



not on that point be deemed otherwise than reliable. The author next addressed 

 himself to the objections raised against conclusions drawn from experiments in 

 ''Multiple" cables. Faraday had. experimented, he said, upon wires laid in close 

 juxtaposition, and with reliable results ; but an appeal was made to direct experi- 

 ment, and the amount of induction from wire to wire was weighed, and proved to 

 be as one to ten thousand, and it was found impossible to vary the amount of 

 retardation by any variation in the arrangement of the wires. Testimony, also, on 

 this point was not wanting. The Director of the Black Sea Telegraph, Lieut. Col. 

 Biddulph, was in England, and present at many of the experiments. He confirmed 

 our author's view, adding, "that there was quite as much induction and embar- 

 rassment of instruments in this cable as he had met with in the Black Sea line.'' 

 The author considers it, therefore, proved " that experiments upon such a cable, 

 fairly and cautiously conducted, may be regarded as real practical tests, and the 

 results obtained as a fair sample of what will ultimately be found to hold good 

 practically in lines laid out in extenso. At the head of each column in the annexed 

 table is stated the number of observations upon which the result given was comput- 

 ed, — every observation being rejected on which there could fall a suspicion of 

 carelessness, inaccuracy, or uncertainty as to the precise conditions ; and, on the 

 other hand, every one which was retained being carefully measured to the 

 hundredth part of a second. This table is subject to correction, for variation in the 

 state of the battery employed, just as the barometrical observations are subject to 

 correction for temperature. Of this variation as a source of error I am quite aware, 

 but I am not yet in possession of facts enough to supply me with the exact amount 

 of correction required. I prefer, therefore, to let the results stand without 

 correction. 



AMOUNT OF RETARDATION OBSERVED AT VA1UOUS DISTANCES. 

 TIME STATED IN PARTS OF A SECOND. 



VOLTAIC CURRENT 



Mean of 



550 

 obsrvns. 



83 miles 

 •08 



Mean of 



110 

 obsrvns. 



166 miles 

 •14 



Mean of 



184-0 

 obsrvns. 



249 miles. 

 •36 



Mean of 



1960 

 obsrvns. 



498 miles. 

 •79 



Mean of 



120 simultaneous 



observations. 



535 miles. 

 •74 



1020 miles. 

 1-42. 



— Now it needs no long examination of this table to find that we have the re- 

 tardation following an increasing ratio, — that increase being very little beyond the 

 6imple arithmetical ratio. I am quite prepared to admit the possibility of an 

 amount of error having crept into these figures, in spite of my precautions ; indeed, 

 I have on that account been anxious to multiply observations in order to obtain most 

 trustworthy results. But I cannot admit the possibility of error having accumulated 

 to such an extent as to entirely overlay and conceal the operation of the law of the 

 squares, if in reality that law had any bearing on the results. Taking 83 miles as ou t 

 unit of distance, we have a series of 1, 2, 3, 6, and 12. Taking 166 miles as our unit 

 we have then a series of 1, 3, and 6. Taking 249 miles, we have still a series of 1, ,2 

 and 4, in very long distances. Yet even under these circumstances, and with 

 these facilities, I cannot find a trace of the operation of that law." The author 

 then examined the evidence of the law of the squares, as shown by the value of a 

 current taken in submarine or subterranean wires at different distances from the 



