322 



NATURE 



[Fed, 8, 187^ 



do not appear to have been attended with similar improvements 

 in the quality of the material as indicated by its chemical com- 

 position, for the highest quality of sheet gutta-percha which Prof. 

 Abel himself had been able to find contained 127 per cent, of 

 resinous matter and 5 per cent, of water. Much greater pains 

 are no doubt taken to consolidate the material and express the 

 water from the gdtta-percha coatings of wire than in the manu- 

 facture of sheet gutta-percha. Nevertheless, that a consider- 

 able amount of inclosed water still remains is evidenced by 

 the fact that in two samples of covered wire, submitted by 

 the same manufacturers as lately as September and Novem- 

 ber last, the one contained i"86 per cent., and the latter 3 '97 

 per cent, of water. Little doubt now remains that the pro- 

 cesses of "mastication" (to which gutta-percha is subjected for 

 the removal of certain impurities and the production of a me- 

 chanically homogeneous material) favours oxidation, so that the 

 destruction of some of the most valuable qualities of gutta-percha 

 as an insulator depend upon the degree of completeness to which 

 the mechanical impurities have been removed. An examination 

 of old gutta-percha seems to show that, provided the material 

 has been reduced to a compact condition, oxidation due to ex- 

 posure to the air and light proceeds but slowly. 



Dr. Miller also points out that mastication promoted the oxi- 

 dation of india-rubbe7-, and further experience has established the 

 similarity of the two gums in this respect. The application of 

 vulcanising to india-rubber was hailed as a most important step 

 in submarme telegraphy ; but although many chemists have 

 made this same process of vulcanising a subject for study and 

 investigation, it remains imperfectly understood even to the pre- 

 sent day. The wire manufacturer had no difficulty in meeting 

 the most important objection urged against the application of the 

 vulcanising process (viz., the injury done to the conductor by the 

 chemical action of the sulphur in the dielectric upon it) by avail- 

 ing himself of the fact that tin would not be equally affected, 

 and so protecting the copper by the simple process of tinning. 

 Still the tendency to an alteration, either in the chemical or 

 mechanical structure of vulcanised india-rubber, exhibited by it 

 when kept submerged in water, has developed serious elements 

 of uncertainty in cables prepared by the vulcanising processes. 

 Prof. Abel then proceeded to give some interesting illustrat'ons 

 drawn from his own personal experience of the uncertainty of our 

 existing knowledge regarding the chemical and other conditions 

 to be fulfilled in the application of vulcanising processes to the 

 preparation of telegraph cables. 



A number of half-mile lengths, for instance, of vulcanised 

 telegraph cable — some for field service, others for firing broad- 

 sides on board ship — were found, after a period varying from 

 eighteen months to three years, to have undergone considerable 

 deterioration ; the dielectric in some instances had become so 

 porous that even the variations in the hygroscopic condition of 

 the atmosphere on board ship, where the wires were placed be- 

 tween decks, caused decided differences in the results obtained 

 with a particular battery power ; and this alteration was not 

 distributed uniformly over a length, the porosity in some in- 

 stances extending along a few feet only, the adjacent portions 

 being in very good condition ; an inspection of a large quantity of 

 the same sort of cable which had remained untouched in store 

 showed precisely similar results. 



The uncertainty attaching to this is still further illustrated by 

 the fact that in armoured cables with multiple cores of this de- 

 scription some of the cores remain comparatively good, whilst 

 the insulation of others had fallen off to a very great extent. 



Scarcely less conflicting is the experience gained with cables 

 prepared according to Hooper's system. This system consists 

 in maintaining the inner portion of the india-rubber surrounding 

 the conductor in an unvulcanised condition by means of a " se- 

 parator," which contains a preparation of a metal possessing the 

 power of arresting the passage of the sulphur beyond it during 

 and subsequent to the application of the vulcanising process. 



The deterioration due to the alteration of the india-rubber 

 being caused by oxidation, the question naturally arises as to how 

 the oxygen finds access to it ? It must evidently find access to 

 the interior of the dielectric through the substance of the cable — a 

 view which is more than confirmed by the researches of Graham. 

 That eminent chemist showed that solid india-rubber absorbed 

 oxygen to an extent which showed the gas to be twice as soluble 

 in it as in water at the ordinary temperature, and the compara- 

 tively greater priority of vulcanised india-rubber would favour 

 this absorption. The oxidation of unvulcanised india-rubber 

 being once established, the tendency to the absorption of oxygen 

 by the external vulcanised india-rubber, and to its passage through 



the latter, must be promoted by the increased tendency to che- 

 mical change of and continual assimilation of oxyt^en by the 

 inner portion, which thus acts like the vacuum by which Graham 

 caused air very rich in oxygen to filter through a stout vulcanised 

 india-rubber tube. 



The efforts made from time to time to improve the insulation 

 of cables, served until lately to clear the ground for future expe- 

 riments, but of late important success seems to have been 

 achieved in a direction where different experimenters (including 

 Prof. Abel himself) had failed — that direction is towards paraffin, 

 " a substance which during the last thirty years had passed from 

 the obscure position of a chemical curiosity to the foremost rank 

 amongst important chemical products." In 1875 Mr. Field, 

 F.R.S., working in conjunction with Mr. Tailing, the mineral- 

 ogist, produced by means of a solvent, or by masticating the sub- 

 stances together, a black ozokerit-product with india-rubber, 

 which appeared quite free from the brittleness which Matthiessen, 

 who also had been at work here, failed to get rid of This pre- 

 paration in point of insulation and inductive capacity compares 

 very favourably with india-rubber and gutta-percha, and would 

 seem likely to prove very valuable for telegraphic purposes in 

 the future. 



Prof. Abel could only allude to the importance of chemical 

 science in the proper management of batteries, a subject which, 

 after the valuable paper read before the Society by Mr. Sive- 

 wright, " On Batteries and their Employment in Telegraphy," 

 and the instructive discussions which it elicited, needed only to 

 be named. Amongst other matters of importance where the 

 telegraph engineer might derive great benefit from the fruits ot 

 applied chemistry, were the decay and preservation of telegraph 

 poles, the preservation of fibrous materials used in constructing 

 submarine cables, the production of points and the protection of 

 cables against the deposition of vegetable or animal growth. 



Prof. Abel then concluded his address by a final illustration of 

 the manner in which the practical electrician may unexpectedly 

 be brought face to face with problems which can be solved by a 

 knowledge of chemistry and by that alone. Lieut. -Col. Stotherd, 

 R.E., having pointed out certain defects in the permanency and 

 difficulties connected with the testing of Abel's "phosphide" 

 fuse, he (Prof. Abel) constructed another form of high tension 

 fuse specially designed for submarine mining. The poles of this 

 new fuse were 0*05 of an inch apart, in an insulating column con- 

 sisting of Portland cement with sufficient sulphur to allow of its 

 being melted and cast in a mould. Fuses manufactured in this 

 way were supplied to different military stations, and after a time 

 it was found that the average resistance of the fuses being 15,000 

 ohms, that of many of them had fallen as low as 300 or 400 onms, 

 and one or two had gone down even below 50 ohms. The cause 

 of this at first sight inexplicable change in the stability of the fuse 

 was traced by Mr. E. O. Brown to the existence in many of the 

 cement pillars of very minute hair-line cracks or fissures extenJ- 

 ing sometimes right across the space between the inclosed small 

 copper wires. The sulphur in the cement and the copper wire 

 in presence of the air which had penetrated with the ever- 

 concomitant moisture had set up a galvanic action which had 

 formed one or more complete bridges, thereby short-circiriting the 

 copper poles. Chemical knowledge, which unravelled this mystery 

 at once, provided the remedy ; platinum, upon which sulphur and 

 air were powerless, replaced the copper, and the permanence of 

 the fuse was secured. 



A hearty vote of thanks to Prof. Abel was carried by acclama- 

 tion, and it was decided that the address should be printed and 

 circulated amongst the members. 



SCHOLARSHIPS AND EXHIBITIONS FOR 

 NATURAL SCIENCE AT CAMBRIDGE, 1877 



'T^HE following is a list of the Scholarships and Exhibitions 

 ■^ for proficiency in Natural Science to be offered at the 

 several Colleges and for Non-Collegiate Students in Cambridge 

 during the present year : — 



Trinity College. — One or more Foundation Scholarships ot 

 100/., and one Exhibition of 50/. The examination for these 

 will commence in the first week of April. 



St. John's College. — One of the value of 50/. per annum. 

 There is a separate examination in Natural Science at the time 

 of the annual College examination at the end of the academical 

 year, in May ; and Exhibitions and Foundation Scholarships 

 ranging in value up to 100/. will be awarded to students who 



