April I, 1884] 



NATURE 



529 



which is at the outside 20 vohs, or about 18 volts as the 

 cells run down. 



In all cases hitherto named an ordinary battery current 

 has been employed. In a paper read by me before the 

 British Association at Southport, I named a rotating 

 commutator and also one on the plan of a metronome 

 which I had tried for the purpose of diminishing currents 

 of polarisation by regular inversion. I preferred, how- 

 ever, the rapid manipulation of an ordinary commutating 

 key with the fingers of the left hand until the " throw" 

 of a damped galvanometer was all but extinguished. 



At the Southport meeting, however, my friend. Dr. 

 Oliver Lodge, suggested the use of alternating currents of 

 induction, and a telephone in place of the galvanometer, 

 and Prof. Lankester. the President of the Section in which 

 my paper was read, kindly suggested that I should apply 

 to the Royal Society for a grant in aid to purchase the 

 expensive apparatus require! for these experiments. 

 The latter suggestion I at once acted on, and met with 

 unconditional refusal on a printed form. Being thus 

 thrown on my own small means, I proceeded to act on the 

 former suggestion, and ordered an induction apparatus of 

 an excellent London maker. But the British workman, 

 if sure, is decidedly slow, and the instrument, though 

 stated to be in a condition of forwardness, is not yet 

 ready. In the meanwhile, in the pages of the Electrical 

 Rcviao for January 12, a diagram, description, and wood- 

 cut of a pretty little instrument designed by Prof. 

 Kohlrausch of Wurzburg for the measurement of fluid 

 resistances appeared ; by his kindness I was put in com- 

 munication with the firm of Hartmann and Co. of that 

 town, the makers. They at once forwarded me the in- 

 strument, which proves to be beautifully made, and 

 extremely moderate in price. This acknowledgment I 

 owe to the Professor's courtesy towards a stranger, and 

 their briskness in carrying out his wishes. Upon its 

 details it is needless now to insist, it being practically 

 a small induction-coil united to a metre-bridge of 

 platinum-silver wire, with resistances of i, 10, 100, and 

 1000 ohms, to be intercalated in the divided circuit. It 

 emits a steady buzz of about 120 vibrations per second, 

 which is reproduced in the telephone by methods well 

 understood. In my first experiments I found the original 

 and the phantom buzz difficult to separate. The former 

 is easily lessened by mounting the apparatus on vulcanised 

 rubber tubing and a solid support. The R. is read off 

 the scale by inspection : towards the left hand or middle 

 of the wire with great accuracy; towards the right-hand 

 end the ohms get squeezed together. When I drew the 

 plug of the 1000 R. my willing student-patient gave a 

 jump out of his two brine baths and said he could not 

 stand it. It was therefore necessary to use the 100 

 ohm plug. Even with this, however, the results 

 were very remarkable. In this early period of my 

 experiments two illustrative cases may be given. A 

 female patient suffering from diabetes, but otherwise 

 in good health, and able to walk about the ward, gave 

 from foot to foot with an E.M.F. of 36 volts, a resistance 

 of 1210 ohms ; from right hand to right foot 1350 ohms; 

 and from left hand to left foot exactly the same figure. 

 With the induction current she gave from foot to foot 

 only 473 ohms ; from hand to foot 735 ohms on the right, 

 and 750 ohms on the left, side. The difference was so 

 great that at first I suspected instrumental error, but sub- 

 sequent testings show that such is not the case. The 

 discrepancy of 15 ohms between the two sides was clearly 

 owing to my unfamiliarity with the telephone in place of 

 galvanometer, and has materially lessened with greater 

 experience. 



A male patient suffering from dysentery, now perfectly 

 well, gave from right hand to foot with a current of yd 

 volts a R. of 1580, with 62 volts a mean of 15 10, with 

 1 8 volts a R. of 1366. E.-ich observation was taken 

 wice ; the first and last agreeing exactly, the intermediate 



only difiering from 1520 to 1500. This is impossible at 

 times to prevent from the unintentional motions of the 

 patient slightly shifting the level of the brine baths. With 

 the same baths and poles the induction current gave only 

 590 ohms resistance. 



In neither of these cases was there any morbid con- 

 dition of the muscles tested. The distance was in each 

 case from the external malleolus of the foot to the head 

 of the ulna in the corresponding hand. In recording 

 these results, I prefer, as on the former occasion, to give 

 them at once in their rough state before waiting for a 

 plausible explanation, or endeavouring to procure a fal- 

 lacious agreement between the two methods. It is clearly 

 not, as a writer in the Electrical Jotcrnal thought, a case of 

 mere "cable-testing." What I stated then I now re- 

 affirm, that there is some important difl'erence of a 

 ph)siological character between the human body as a 

 conductor and ordinary fluid electrolytes. 



No doubt, as Dr. Lodge suggests, ■' an alternating 

 current ought to show too low a resistance, because of 

 electro-chemical capacity, which it would treat like con- 

 ductivity.'' But the diflerence is far too great for such 

 an explanation, nor does it occur to this extent in saUne 

 solutions. I am at present engaged in testing its amount 

 in physiological fluids, such as blood-serum, ascitic and 

 ovarian effusion, and the like. 



A beautiful metre-bridge on Prof. Kohlrausch's pattern, 

 with platinum-silver wire of 3 m. long, has just reached 

 me from Hartmann ; with this I am using a "sledge" 

 inductoriurn of Du Bois Reymond's with three different 

 secondary coils of dift'erent lengths and fineness of wire. 

 For the determination of the alternating currents passing 

 I am using the small dynamometer with aluminium wire 

 suspended coil which was shown before the Physical 

 Society, and briefly described in NATURE. 



This I shall check by a fine instrument now on its 

 way from Wurzburg, with a single wire suspension and 

 torsion head instead of the more sluggish bifilar method. 

 Ultimately it may be necessary to use a quadrant electro- 

 meter. 



Even at this stage it is obvious that the fact of the 

 human body being about twice as permeable to induction 

 as it is to low tension continuous currents is of great 

 physiological and therapeutical importance. 



W. H. Stone 



EXTERN ATIONAL WEIGHTS AND 

 MEASURES '■ 

 A LTHOUGH to some it might appear that the work 

 ■^*- of the Bureau at Sevres is perhaps proceeding 

 slowly, yet by reference to the two publications which 

 have been issued under the authority of the Comite In- 

 ternational it may be seen that the Bureau is doing its 

 work thoroughly. The extent of the questions investi- 

 gated is well shown in the first publication issued in 

 1881 (tome i.), which included papers by the director. 

 Dr. Broch, on the force of gravity, the tension of vapour, 

 the boiling point of water, and the weight of a litre of 

 air ; as well as independent investigations by Dr. Benoit 

 on Fizeau's dilatometer ; by Dr. Pernet, on thermome- 

 ters ; and by M. Marek, on weighing apparatus, &c. 



The present publication (tome ii. 1883), to which we 

 would now invite attention, contains accounts by Dr. 

 Benoit of his expansion experiments ; by M. Marek, on 

 the methods and results of the weighings made at the 

 Bureau from 1879 to iSSi ; and by Dr. Broch, on the 

 expansion of mercury. In the experiments on the 

 dilatation of standard measures of length, there has 

 been followed a method attributed to General Wrede. It 

 consists in the first instance in adjusting under two micro- 

 meter-microscopes a platinum-iridium bar, on which the 



' " Bureau International des Poids et .Mesures." TraT'.iu-r ft Itlemoin-s. 

 tome ii.. 400 pp. Pans. 18S3. 



