382 



NATURE 



{August 30, 1877 



abundant in the brine-pans at Lymington at the present day. 

 Branchifnis, or Chirocephalus, is a freshwater crustacean found 

 living in ponds in Devonshire and Kent. Its preservation is due 

 to the admirable nature of the fine argillaceo-calcareous rock, 

 in which it lias been entombed in such numbers, the delicate 

 outline of its gill-feet being stained with iron, so as to be as well 

 shown as in a pliotograph. 



■SECTION G.-MECitANic.\L Science. 



On Compouml TniUncs, by Prof. Reynolds. — The combina- 

 tion of centrifugal pumps not having hitherto produced the 

 anticipated result':, the author had endeavoured to discover the 

 cause of the apparent anomaly, being satisfied that tlieoretically 

 the increase in the number of pumps should produce a propor- 

 tionate increase in the quantity of water raised. Propeily con- 

 necting his pumps, the result was as theory had justified him in 

 expecting ; and the reason why others had failed to attain the 

 same end was that the supply of water had not been adequate, 

 and air had got in instead of water. 



On the Diffin-nce of the Steering; of Steamers with the Screw 

 reversed -ohen under Full Way, and when Moving Slozt<ly, by 

 Prof. Osborne Reynolds. — Referring to the Report on this sub- 

 ject the author 5 aid the fact that the results which had been 

 established by the Committee were so little known to pilots and 

 seamen, besides being likely to excite surprise, would tend to 

 cast a certain amount of discredit, if not on the truth of the 

 results themselves, at least on their importance. It seemed as 

 if nautical men must have formed their opinions from experience, 

 and such was the faith of the English people in the practical 

 that it was very difficult indeed for them to believe that a few 

 landsmen, calling themselves scientific, could teach sailors how 

 to steer ships. .So strong was this feeling that it was to col- 

 lisions they must look in the hope of preventing collision?. This 

 sounded like a bull, but it was perfectly true, for nothing but 

 disasters would awake our rulers to the idea that something was 

 wrong. Fortunately, or unfortunately, such disasters were not 

 wanting. There were the cases of the Ville du Havre and the 

 Locli Earn, in which the collisions were undoubtedly due to the 

 steamers having turned in the opposite direction to that intended. 

 These and other disasters furnish evidence enough of the mistakes 

 which had been perpetrated, and of the importance as well as 

 the truth of the results the Committee had established. He 

 fancied that the ignorance which existed was due to the fact that 

 few seaa^en had turned a ship under full way with the screw 

 reversed, and contented themselves by arguing as to what must 

 happen in such a case from their experience in manceuvring their 

 ships when moving slowly. Of such manoeuvres they had had 

 abundance, but as soon as they got beyond their experience, they 

 adopted the seemingly obvious, but entirely erroneous opinion 

 that the way of the ship would cause the rudder to act as if she 

 was going ahead in spite of the screw being reversed. He felt 

 Jtrongly that in speaking thus in a town like Plymouth he ran 

 the risk of being looked upon as impertinent. If he were wrong 

 he was impertinent, and no one would feel it more than he 

 should. It was not a pleasant task to point out imperfections, 

 however accidental they might be. Even if one saw the wheel 

 coming off an omnibus, all the thanks he was likely to get for 

 pointing it out to the conductor was to be asked if he could not 

 tell him something he didn't know. Of course they must learn 

 as they went on, and all he, with deference, asked of seamen 

 was to try the experiments for themselves, and then aid the 

 Committee in bringing facts under the notice of the Legislature. 

 Their own interests demanded this, for as tilings now were great 

 injustice might be done to the captain who in a case of emergency 

 adopted the very best course to save his ship. 



Mr. William Froude thought the question which Prof. Reynolds 

 had so ably dealt with of immense importance, and deserving 

 minute consideration. Having himself had some experience of 

 small steam launches, he had been surprised at the effect pro- 

 duced by the working of the screw, so that he concurred with 

 the conclusion at which Prof. Reynolds individually, and the 

 Committee collectively, had arrived. If sailors would occasion- 

 ally listen to the advice of outsiders, it would do them no harm. 

 Ignorance as to the effect of reversing the screw upon the way 

 of a ship would often lead a captain info danger which might be 

 avoided. 



Sir William Thomson urged that the Committee should be 

 reappointed, so that the Admiralty might have another oppor- 

 tunity of confirming or refuting the conclusions. This was 



undoubtedly nothing less than a national question, for the con- 

 flict now going on between Russia and Turkey proved that skill 

 in manceuvring was of vital importance in torpedo warfare. In 

 olden times the glory of Engl.ind was maintained by the facility 

 with which her ships were manreuvred, our navy being a match 

 against the navies of all the world in this respect, and he hoped 

 nothing would occur to destroy that pre-eminence. 



• On the Resistanee of Ships, by Mr. William Froude, F.R.S.— 

 The object of the paperjwas to show the effect produced on the 

 resistance to a ship's motion by the lengthening or shortening of 

 the Hat middle body between the bow and stern. The results 

 were based upon experiments made at Chelston Cross with 

 models h.iving the same ends, but different lengths of parallel 

 holy inserted amidships. By separating the effect of the fric- 

 tional skin resistance, which w.is proportional to the wetted 

 snrface, he proved that the increase or diminution of the power 

 required to propel a ship, in consequence of the alteration of the 

 length of the parallel body, depended very largely on the coin- 

 cidence, or want of coincidence, of the wave crests travelling 

 alongside the ship with the points at which the reduction of 

 breadth by the fine lines began. When this diminution coincided 

 with a wave crest there was no loss, but rather a gain of speed ; 

 while when it coincided with a wave hollow the loss of speed, or 

 increase of resistance, was considerable. 



The Elevated Railway of^ New }'<;;/;•, by Capt. Douglas Galton. 

 — The first portion of this railroad was completed for steam- 

 traction at the beginning of 1S72, and was originally constructed 

 for a rope railway, which did not prove successful. This section 

 consisted of single " Phcenix " columns, nine inches in diameter, 

 spaced from 26 to 30^ feet apart along the .axis of the roadway, 

 and carrying two pairs of rolled deck or " I " beams of shallow 

 depth, one pair under each rail. This structure w.as origin.ally 

 deficient both in vertical and lateral stiffness. The deflections 

 of the girders were too great, .and the oscillations of the columns 

 too large. In the nextalterationthe columns consisted of clusters of 

 round solid wrought iron bears, four and a quarter inches diameter, 

 grouped by two and by four, braced together so as to form a 

 single support, and carrying rolled channel bearers, two under 

 each rail. The bars were bent so as to branch like a V at the 

 top, the columns composed of two bars forming a bracketed 

 support under the beams, and those composed of four bars giving 

 longitudinal stability to the structure. Although imperfect and 

 needlessly expensive, this style of column might be considered 

 the parent of all subsequent improvements, and to have furnished 

 a valuable hint for future designs. The line was single with 

 sidings to allow trains to pass. Its length, including the sidings, 

 was l\ miles, but it was now proposed to double the line 

 throughout and extend it. The atmospheric brake, which was 

 in use upon aU trains on the line, placed them entirely under the 

 control of the engineman, and was so effective that a train 

 moving at a maximum speed could be brought to a full stop in a 

 distance barely exceeding its length. The cost of this elevated 

 railway for a double line was estimated at about 55,600/. It 

 was simple in construction, and did not much interfere with 

 street traffic in erection ; it was very economical as compared 

 with underground railways ; it was pleasant to travel on ; and it 

 was comparatively free from risks of accident from collision ; it 

 was easy of access ; the form of locomotive adopted was free 

 from objection, as it was comparatively noiseless and did not 

 appear to frighten horses when passing above them, and on the 

 whole was more free from objection than any other form of road 

 for rapid transit in towns. 



Mr. G. Stephenson followed with a similar paper On a Naa 

 Safety Suspe)ision Trannmy or Light Railway. 



'J he Iniportaneeof giving a Distinctive Character to the N'ecJles 

 Light, by Sir Wm. Thomson, F. R.S. — He urged the necessity 

 of giving a distinctive character to different classes of lighthouses, 

 referring more particularly to the Needles light. He contendeil 

 that the period of no revolving light ought to be more than half 

 a minute, and stated that the three minutes revolving lights on 

 the Irish coast had been done away with, and periods of a 

 minute and half a minute substituted. To every fixed light a 

 distinctive character should he given. Nine- tenths of our light- 

 houses had fixed lights, which had the advantage of being 

 continuously visible, but lost the advantage of the great 

 intensity of the revolving light. The distinctive character which 

 he suggested should be given to the Needles and similar light- 

 houses was similar to the signals invented by Capt. Colomb, but 

 instead of short and long flashes, he proposed to substitute short 

 and long eclipses. 



