i84 



NATURE 



{Dec. 28, 1876 



Telegraph Company (which had been encouraging 

 experiments), had succeeded in effecting a balance, in 

 1873, on the Gibraltar- Lisbon cable by the use of the 

 Wheatstone balance method and Varley's artificial line. 

 Also, in a letter to the Telegraphic Journal for 1874, by 

 Mr. B. Smith, of the Eastern Telegraph Company, we 

 learn that he had succeeded in effecting a balance 

 on one of the Company's cables between Malta and 

 Alexandria in July, 1873. so that he could receive mes- 

 sages while sending a distance of 911 nautical miles. 

 In September of the same year Mr. Smith also reported 

 good success on the Malta-Gibraltar cable, a distance of 

 1,121 nautical miles. We are not aware, however, that 

 these methods have been in practical working for any 

 length of time. 



In 1874 Mr. John Muirhead, of the firm of Messrs. 

 Warden, Muirhead, and Clark, telegraph engineers, West- 

 minster, took out a patent for a new form of condenser, 

 or inductive-resistance, so made as to imitate a submarine 

 cable, and ostensibly for the purpose of duplex tele- 

 graphy. The inductive resistance is formed by taking 

 two strips of tinfoil and laying one over the other sepa- 

 rated by an insulator. One strip forms the conducting 

 circuit of the artificial line, the other forms the outer, or 

 inductive coating, and is connected to earth. The current 

 is passed through the conducting strip and exposed 

 throughout its entire length to the induction of the other 

 strip or sheet in the same way that the current in the con- 

 ductor of the cable is subjected to the induction of the 

 earth throughout its length. The principle of Muirhead's 

 artificial line is shown in Fig. 7, where the arrows repre- 

 sent the local current passing along the conducting strip 

 while being at the same time retarded by the induction of 

 the other strip, or inducting plate, which is connected to 

 earth. 



This artificial, or model cable, can be made to have the 

 same resistance, capacity, and even leakage, per knot, that 

 the actual cable has, so that it can be made practically 

 equal in its electrical properties to the actual cable. It 

 may be employed either with the differential or Wheat- 

 stone balance methods. In either case the local current 

 passes through the conducting strip to earth, experiencing 

 the same resistance and retardation that the signalling 

 current experiences in the cable. It therefore balances 

 the signalling current in its effects on the instrument. Its 

 advantage over Varley's " artificial line " consists in the 

 closer equivalence to an actual cable that it admits of. 

 Subsequent patents of Mr. Muirhead describe various 

 adjustments to be used in connection with the artificial 

 line for the purpose of refining upon the balance. 



In July, 1875, this system, which is hitherto the 

 most successful of all in submarine duplex, was first tried 

 on Jhe Marseilles-Bona (Algeria) cable, a length of 448 

 nautical miles. In the spring of this year it was esta- 

 blished for permanent working on the Marseilles- Malta 

 cables of the Eastern Company, a length of 826 nautical 

 miles, and also on the Suez-Aden cable, a length of 1,461 

 nautical miles, but in an electrical sense, one of the 

 longest of existing cables. These are the first practical 

 successes in submarine duplex telegraphy, and they also 

 prove the feasibility of working cables of any length by 

 th s advantageous method. 



MUSEUM SPECIMENS FOR TEACHING 



PURPOSES 1 



II. 



A RTICULATED or mounted skeletons are divided into two 

 "^ classes: l. Natural ; 2. Artificial. The two processes may, 

 however, be more or less combined in certain cases. 



Natural skeletons are not macerated. The bones are merely 



' Lecture at the Loan Collection of Scientific Apparatus, South Ken- 

 sington, July 26, 1876, by Prof. W. H. Flower, F.R.S., Conservator of the 

 Museum of the Royal College of Surgeons of England. Continued from 

 p. 146. 



cleaned by the hand, assisted by scalpel, scissors, and brush ; 

 the subject being placed in water during the intervals of the 

 operation, to get it free from blood, and to soften the parts re- 

 moved. Everything having been taken away, except the bones 

 and the ligaments which unite them, the skeleton is fixed in the 

 required attitude by external supports, and allowed to dry. This 

 process is commonly adopted with very small mammals, birds, 

 reptiles, and especially fish. It has the advantage of involving 

 less labour and skill in articulation, and of affording a trust- 

 worthy record of the number and relations of the bones, espe- 

 cially the vertebrae, about which, in an artificially articulated 

 skeleton, urdess prepared by very competent hands, there always 

 may be doubt. On the other hand, such skeletons are far less 

 useful for the study of the details of their structure, they not 

 only cannot be taken to pieces, but the extremities of the bones 

 are actually concealed by the dried ligaments. The latter, more- 

 over, often become brittle with time ; and in the case of the 

 smaller specimens, will break unless handled with great care. 

 In such cases it is often advisable to strengthen them with 

 isinglass, or when more support is required, some strands of 

 cotton-wool steeped in melted isinglass or glue make excellent 

 artificial ligaments. 



2. Artificial skeletons are those in which the bones have all been 

 separated and completely cleaned by maceration, or one of the 

 processes substituted for it, and then joined together again by 

 wire. The reconstruction of such skeletons is technically called 

 "articulating." To perform it properly som2 knowledge is 

 required of osteology, so that the bones may be placed correctly, 

 which of course is of the utmost importance, and also some 

 mechanical skill in drilling the holes in the bones, and in adapt- 

 ing and fitting the wires and metal supports, and several instru- 

 ments are required, not needed in the preparation of natural 

 skeletons, such as drills, pliers, wire-cutters, files, &c. 



The best wire is iron-tinned, which does not rust, and is now 

 sold at most ironmongers. For very fine work, iron wire plated 

 with silver, and for still more delicate operations, especially in 

 fishes' skeletons, thin silver wire may be used. Copper wire 

 is too soft and flexible for almost all articulating work, and is 

 apt to give a green stain to bones which contain any grease, and 

 so should be avoided. Brass tubing of various sizes is now ex- 

 tensively used in articulatiog, and for larger animals, iron sup- 

 ports, which will have to be made by the blacksmith specially 

 for each subject. 



However great the knowledge of the articulator, it is always 

 best to take precautions before macerating an animal, that there 

 should be no mistakes in arranging the bones properly, especially 

 in the case of rare and little-known specimens. The skin and 

 the greater part of the soft parts having been removed, and the 

 bones roughly prepared as for a natural skeleton, should then 

 be divided into several parts. The sternum with the costal car- 

 tilages should be removed by cutting through the latter at the 

 junction with the ribs, and cleaned in water without macerating, 

 and then allowed to dry in their natural form on a block of wood, 

 cut to the requisite shape and size. If this part goes into the 

 macerating vessel, the cartilages will be lost, and the thorax can 

 then only be restored in an imperfect manner. The limbs 

 should be separated, and if each is macerated in a separate 

 vessel, much trouble will be saved in sorting the small bones of 

 the feet. If there is any doubt about articulating them correctly, 

 it is best to take them out before they have actually separated, 

 and clean them off and articulate them at once, at all events 

 drilling the holes for the wires while they are still in natural 

 apposition. The vertebrae may be allowed to come apart and 

 macerate together, as there is never any difficulty in placing 

 them in their natural sequence. The hyoid bones should be 

 sought for in the throat, and cleaned and preserved separately, 

 and small sesamoid bones about the feet and behind the knee- 

 joint in most animals, so commonly lost in museum specimens, 

 should be looked for and preserved, as well as the rudimentary 

 clavicles of the carnivora and the pelvic bones of the whales and 

 porpoises. When the relations of any bone to another, espe- 

 cially of the sesamoids above spoken of, or the chevron bones 

 under the caudal vertebrae, are likely to be lost in maceration, 

 they should always be observed, and either notes or drawings 

 made of them, or they should be rrarked with fine holes, made 

 with an Archimedian drill (an essential instrument to the articu- 

 lator). By makmg two holes on different bones opposite to 

 one another before the bones are separated, or several holes ar- 

 ranged in patterns, most important records can be preserved, and 

 such small holes do not damage the bones, as they can be filled 

 up afterwards with putty, or fr9.m!e-m^kers' composition. 



