6i4 



NA TURK 



[April 25, 1895 



Major Cardew's report on the inquiry which he has made 

 into the circumstances connected with a series of explosions 

 which occurred on February I, on Southwaik Bridge, has just 

 been printed x-; a Parliamentary Paper. It will be remembered 

 that there were four explosions ; the first, and by far the most 

 intense, occurred in the culvert under the pavement and road- 

 way on the west side of the bridge, and it was immediately fol- 

 lowed by three explosions in the street boxes of the Electric 

 Lighting Company, on the east side of the bridge. On 

 opening the ground over the culvert, shortly after the explosions, 

 a large crack was found in the 3-inch gas main, out of which 

 the gas was coming in volumes. How the gas was fired could 

 not be exactly ascertained, but Major Cardew confidently 

 asserts that it was not by means of the electric lighting mains. 

 The most striking features about the accident seem 

 to be: (l) The distance to which it appears that a 

 series of explosions may travel along the electric mains 

 which form a gigantic network under the whole of the 

 streets of the city ; and (2) the proof it affords of the in- 

 sufficiency of any ordinary system of ventilation of these pipes 

 and street boxes, if gas can find an easy access to them, and 

 the necessity of exercising great care to make and keep the 

 street boxes impervious to gas. In a former report it was 

 recommended that " accumulation of gas should be prevented by 

 thorough ventilation, by makmg the sides and bottoms of street 

 boxes impervious to gas, and by fillmg up the boxes as far 

 as practicable with incombustible material " ; to this Major 

 Cardew now adds — " by thoroughly plugging pipes and conduits 

 at each street box to prevent passage of gas along the system," 

 and he puts the filling up the boxes first, as the most simple 

 and certain method of preventing danger of explosion. It is 

 admitted that the main c.iuse of the explosions was the defect in 

 the gas-pipe, and this again directs attention to the very serious 

 danger to the public arising from the condition of the gas-pipes 

 in many districts, and the way in which they are laid and 

 supported ; a danger which is continually increasing, owing to 

 the spread of the use of wood paving and other impervious 

 sui faces, and which is temporarily intensified' by every severe 

 frost. No want of care on the part of the gas companies can, 

 however, relieve electric lighting companies of the duty of 

 sufficiently protecting their conduits and street boxes against an 

 accumulation of gas, by acting on the recommendations made. 



It is very commonly believed that in Ireland, on account of 

 the mild climate, the Arctic or Mountain Hare does not turn 

 while in winter, but remains in its brown summer fur. Writing 

 in the Zoologist, Dr. R. F. ScharfT brings evidence that there is 

 no change in the colour of the Irish hare in most winters. But, 

 on the other hand, Major-General Warrand states that — "At 

 Fionebrogue, near Downpatrick, a very large number of hares 

 are taken or killed every year, and it is found that a consider- 

 able number of them turn very white in the winter, while nearly 

 all assume a much lighter shade of fur when the cold weather 

 sets in." The editor of the Zoologist says that this view is sup- 

 ported by a number of sportsmen and good observers, and that 

 he himself has shot several Irish hares in all stages of change 

 from brown to white. 



There is an interesting paper in the Eleclrician, by 

 Messri. Campbell and Lovell, on the supposed magnetic 

 fatigue. Prof. Ewing has recently shown that in the case of 

 good wrought iron, when subjected to very many reversals in 

 weak magnetising fields, there is no perceptible change in the 

 magnetic qualities. The authors have made use of strong 

 magneti>ing fields, and have experimented on cast as well as 

 wrought iron. The specimens to be tested were in the form of 

 ringi wound over with primary and secondary coils. A single 

 B.H. curve wxs taken by the oidinary ballistic method, and 



NO. 1330. VOL. 51] 



then an alternating current of about X'i, amperes at S3 alter- 

 nations per second was kept passing through the primary coil 

 for nearly a month. Another series of tests were then made, 

 and it was found that the B.H. curve obtained coincided exactly 

 with that given before the repeated reversals, both in the case of 

 wrought and cast iron. 



The current number of Wiedemann's AnnaUn contaiiis a 

 paper, by Ilerr A. Bock, on the ratio between the Literal con. 

 traction and the longitudinal dilatation (Poisson's ratio) in 

 magnetised iron rods. In the method employed the rod under 

 test is rigidly supported at its middle, so that it lies in 

 a horizontal plane. At either end of the rod a cross-piece is 

 attached, as well as a plane mirror. These cross-pieces serve 

 as lever arms, from the ends of which weights can be hung. In 

 this way the bar is both bent and twisted, the amount of bend- 

 ing and twisting being read oft by means of a vertical tele- 

 scope, two scales at right angles, and the mirrors attached to 

 the ends of the rod. The difference of the readings on the 

 scale parallel to the length of the rod (B) is proportional to the 

 bending, while the difference in the readings on the scale at 

 right angles to the length of the rod (T) is proportional to the 

 twist. Then using Kirchhoff's formula, Poisson's ratio is given 



by /I = . - - I, where -s is the half length of the rod, and 



/ is the length of the lever arm, at the end of which the deform- 

 ing weight acts. Neither in the case of hard steel or soft iron 

 (a magnetising coil being used in this latter case) was a differ- 

 ence in Young's modulus, or of the torsional rigidity greater 

 than 05 per cent, observed. In the c-ise of soft iron, the author 

 considers that his experiments are sufficiently accurate to show 

 that after magnetisation the torsional rigidity and Young's 

 modulus both diminish. Since, however, B diminishes laster 

 than T, the value of Poisson's ratio increases. The author 

 finds that frequent magnetisation and deformation causes the 

 differences in the elastic constants between the magnetised and 

 unmagnetised states to diminish, and he therefore concludes 

 that it is not possible to detect the effect on the elasticity of 

 magnetisation in a rod by the change in the pitch of the note it 

 emits when struck. 



The field experiments now in progress in various parts of the 

 country partake rather of the character of demonstrations than 

 of incursions into. the domain of original research. The ex- 

 periments made in Carnarvonshire last year, in connection with 

 the agricultural department of University College, Bangor, in- 

 cluded a serici in which a mixture of rye grass and clover seeds 

 was pitted against mixtures containing the seeds of other grasses 

 than rye grass, in addition to or exclusive of the latter. The 

 crops were cut in July, and weighed green, when the crop con- 

 taining clovers and rye grass only was found to be the heaviest. 

 All the plots are to be grazed for the next three years, and it is 

 obvious that considerable time must be allowed before definite 

 conclusions can be arrived at. Experiments made in Anglesey 

 " to test the best quantity of seed to sow for oats," appear pro- 

 visionally to demonstrate that four or six bushels of seed (black 

 Tartarian) broad-castcd per acre, give better crops than are 

 obtained from eight bushels of seed, the quantity sown under 

 the usual practice of the island. In both counties comparative 

 manurial experiments are in progress upon pasture land and 

 field crops. 



The work of the Aberdeenshire Agricultural Research 

 Association in 181J4 was largely concerned with an inquiry into 

 "degeneration of rye grass and passible recovery." It isargued 

 that, in permanent pasture, "starvation of plants, and non- 

 utilisation of the plants when grown, are the features to be 

 remedied, in order to secure permanent pas'.ure of the valued 

 ryegrass." The supreme value of I.olium pcrenne in pastures. 



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