284 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[A I' GUST, 



nearly that of continuity, very uiucli resembling that of a fixed star of the 

 first magnitude. The only difference in the quality of the light is, tliat the 

 lenses being in motion, it resembles a star twinkling violently; and when at 

 rest, it resemljles a planet. The dilTerencc of intensity had been measured 

 by examining the light through a number of plates of stained glass. Some 

 eyes had seen the light through 13 glasses, the lenses being at rest — and 

 through 12, the lenses being in motion; other eyes with other glasses had 

 seen it through 10, the lenses being at rest — and 8, the lenses being in 

 motion. He had seen it through 9, the lenses being in motion, and tbra\igh 

 10 at rest. lie dirl not pretend to say whether mechanical difticulties might 

 not prevent the adoption of the system ; what he aimed at was to establish 

 the principle, that by putting a system of lights into a rapid rotary motion, 

 a continuous light visible in all directions would be the result, without any 

 essential diminution of brilliancy, as compared to that of the same lights 

 when viewed at rest. If this principle shoidd prove correct, its application 

 to practice might afterwards be thought of, and left to the ingenuity of the 

 engineer ; but if the principle should not be correct, and there was a great 

 loss of light by the rotary motion, then it would be tiseless to go on. 



At the subsequent meeting. Feb. 18, Mr. Parkes observed, that he could 

 entirely confirm the account of the experiments with revolving lenses given 

 by Captain Basil Hall on a preceding evening. It appeared to him, that when 

 the lenses made 32 revolutions, the light was not quite continuous ; but at 

 40 revolutions it was perfectly so, although the general effect was twinkling. 

 The central spot was very distinct ; he saw the light equally as distuictly 

 through 10 coloured glasses, the lenses being in motion, and through 11, the 

 lenses being at rest. He would suggest, whether the tremidous appearance 

 of the light might not be in part accomited for by the slightness of the re- 

 volving frame, which, at the required velocity, vibrates considerably. In the 

 temporary ajiparatus erected at the Tower, one man coiUd iriaintain about -40 

 revolutions per minute. 



Jlr. Alexander Gordon remarked the coincidence of the experiments of 

 Captain Basil Hall with a law of light as laid down by writers on optics, — 

 viz. that if a luminous body pass the eye eight times in one second, the im- 

 pressions are blended so as to produce the appearance of continuity, or that 

 the duration of an impression on the retina may lie taken at about eight 

 seconds. Xow, in the apparatus erected by Captain Basil Hall, there are 

 eight lenses, and continuity of light is produced when the frame makes 60 

 revolutions a minute. Thus, eight lenses flash across the eye in one second, 

 and the observed residt is a remarkable confirmation of the law alluded to. 



Mr. Hawkins thought the light was better and steadier at 40 revolutions 

 than at any other speed. ^A'hen observing the reflection of the light on the 

 features of the by-standers, he saw them very distinctly, the lenses being at 

 rest ; Iiut from the moment of commencement of motion, there was a visible 

 fliminution in the intensity of the light, which increased with the speed. He 

 saw the light, the lenses being at rest, through 10 coloured glasses, and 

 through 9 when in motion. 



Jlr. Macneil! thought the light was steadier at GO than at 40 revolutions. 

 The shadow was less intermittent. He did not conceive the mode of examin- 

 ing the intensity of the light through coloured glasses to be so con-ect as by 

 observing tlie depth of the shadow, as the eye was capable of judging more 

 correctly of the relative intensity of shadows than of lights. M'hen the lenses 

 were in rapid motion, there appeared a dark spot in the centre of a luminous 

 jiisc. 



Professor Keating, of Philadelphia, stated that the dark sjiot in the centre 

 appeared as if he saw the wick of the lamp. The lenses being at rest, the 

 light was uniform ; but on their acquiring a certain degree of velocity, its 

 whiteness diminished ; until at 40 revolutions a decided orange tint appeared, 

 and at (10 revolutions both the orange hue and the centre dark spot in- 

 creased. 



Mr. Lowe inquired whether the quantity or intensity of light was mos' 

 required for lighthouses. The conflicting opinions of experimenters on the 

 intensity of light, as ascertained by the photometers now in use, show that 

 some better test or means of comparison is wanted, lie should conceive 

 that pieces of coloured glass could not afford any accurate measurement of 

 the space-penetrating power of light at so small a distance as 345 feet, which 

 he underst lod was the length of the room in which these experiments were 

 tried. The depth of shadows also furnished no adequate measure of the iu- 

 tensity of light, for shadows were differently colom'cd for difltrcnt lights. 

 Perhaps the photogenic paper might furnish the tests and means of com- 

 )>arison now so much wanted. 



The President remarked on the advantages of the revolving lights, as apar* 

 from the greater IjriUiancy, in that they are pecidiarly useful as being easily 

 distinguished from land and other lights, which tend to mislead mariners. 

 There may be peculiar advantage in the tremidous character of Captain Basil 

 Hall's liglit, as enabhng it to be more easily distinguished among others. It 

 is not simply the quantity of light which is diffused over the horizon which 

 is valuable, but the intensity of the ray in a certain direction, which, faUing 

 on the eye, rivets immediate attention. 



Feb. 25. — The President in the Chair. 



The following were balloted for and elected : — William Reed, Captain An- 

 drew Henderson, Edward Oliver Manby, WilUam Johnson, Alfred King, and 

 Gnstave Holtze, as Associates. 



" Oil the Iiiijirurenimt of Xai-iyalle Jiioers, u-ith a Descriji/ion of a self- 

 nc/iiiff Vaslcloard at Nahurn Lock, on the River Ouse." By Henrv Kenton, 

 Crad. Inst. C. E. 



Previously to the year 1834, the navigation of the Kivcr Ousc from Selby 

 up to Boronghbridge, a distance of 39 miles, was much impeded by a num- 

 ber of shoals or " huts," some of tliem of considerable extent — all vessels 

 drawing more than 5 feet water being compelled to await until the spring 

 tides set in, so as to afford them sufficient depth of water. Mr. Rhodes was 

 consulted as to the best mode of obviating this difficulty. He recommended 

 the employment of a steam dredging-maehine to deepen the bed, by removing 

 the shoals, and the construction of a self-acting wastehoard on the dam, so 

 as to give an additional height of water between Naburu and Linton Locks, 

 as it was found that no injury could occur in the adjacent lands from the 

 level of the river being raised 18 inches. 



The greater part of the shoals consisted of compact blue clay, with a mi.\- 

 ture of gravel and large boulder stones, and, in a few instances, of oak trees, 

 such as are found near the bottom of bogs. 



To use the dredging-maehine in the most advantageous manner, the prin- 

 ciple of the sliding tool in a turning lathe was adopted, by running the ma- 

 chine across the face of the shoal from side to side of the river, without al- 

 tering the position of the lower tumbler. This method produced a perfectly 

 even horizontal surface of the bed, and prevented subsequent accumulation. 

 Tlie whole of the shoals were thus removed, so that sea-borne vessels and 

 steamers, drawing from 11 to 12 feet water, could at all periods navigate to 

 York, a distance of 80 miles from the Ilumber. It was still necessary to 

 raise the height of the water at least 18 inches between Naburu and Linton 

 Locks, to enable vessels drawing 7 feet water to pass at all seasons from 

 York up to Boronghbridge, a farther distance of 20 mUes. To accompUsh 

 this, the self-acting wastehoard was constructed. 



It is composed of two distinct boards of Jlemel timber, each 76 feet long, 

 18 inches high, and 4 inches thick, placed on the top of the angular face of 

 the dam. It is fixed by means of strong wrought-iron hinges, leaded into 

 the stone work at inter\als of 10 feet. Over the hinges are fixed wrought- 

 iron bolts, 1 inch diameter, connected by flat chains with the plimmer blocks 

 on a line of shafts extending behind eacli board on the face of the dam ; on 

 the ends of these shafts are fixed spur-wheels working into iiiuions which 

 drive pulleys, over which run tlie chains supporting the balance weights, 

 which are bung on the face of the A\ing walls. AVhen the balance weights 

 are at the bottom of the walls, the wastehoard will be in an upright position, 

 which occurs wlien the surface of the water does not rise 6 inches above the 

 top of the boards or 2 feet above the dam ; but when, on a sudden increase 

 of the volume of water, there is a considerable pressure on the face of the 

 wastehoard, it more than counterbalances the weights, and causes the boards 

 to incline towards a horizontal position, at the same time raising the balance 

 weights and allowing a free passage for tlie water. \Vlien the pressure di- 

 minishes, the weights descend and the boards resume their vertical position. 



The time occujiicd in dredging the river and constructing the wasleboards 

 was two vears, and the cost of the latter, which was made bv Messrs J. and 

 ^\. Laildcr, of York, was £300. 



The result of these alterations has been most satisfactory, as, since their 

 completion, not a vessel has been detained in the upper level, and the regis- 

 ters of the heights of the water at Linton and Nabin-n Locks and York show, 

 that the winter floods have not risen to such a height, or continued for so 

 long a period, as previously to the improvements being carried into effect. 



" On the autogenous unitinr/ of Lead and other metals." By M. Delbruick 



The term " autogenous " is employed by the inventor, >L de Richemont, 

 of the method now described, to designate the union of pieces of metal of the 

 same kind with one another, without the intervention of the ordinary alloys 

 of tin or other connecting medium. This is effected by directing, by means 

 of a fine beak, the flame of a jet of hydrogen on the parts to he united. A 

 complete fusion of the metal is thus efi'eeted, and the parts are united in one 

 homogeneous mass, the metal at the points of junction being in the same 

 state chemically as at the parts untouched. Plates of any thickness, whatever 

 the direction of the edges to be joined, may thus be perfectly united, and the 

 lines of junction made as strong as the rest of the mass. Many circumstances 

 contribute to render the joints made with common solder objectionable. The 

 rates of expansion and contraction on changes of temperature for lead and 

 its alloys with tin are different ; some chemicil agents act much more on 

 alloys of lead and tin than on lead alone. The alloys also are fragile, and 

 the solder may not perfectly attach itself, without the imperfection being 

 observed. In addition to obviating these objections, M. de Richemont con- 

 ceives that his new method or union possesses the farther advantages of 

 economy, in saving of solder and in avoiding seams and overlappings ; in per- 

 mitting the use of thiimer lead and the use of lead where it is now inad- 

 missible, and in rendering practicable the repairs of vessels which are now 

 impracticalde. 



M. de Richemont also applies this jet of flame to heating the common sol- 

 dering irons used by tinmen and plumbers. The jet is permitted to play 

 upon the tool, which, in a few seconds, is brought to the requisite beat, and 

 maintained at that heat without any injury to the tool. The heat can be 

 regidated to the greatest nicety by diminishing or increasing the jet. The 

 author conceives that the sulphate of zinc produced in the manufacture of 

 the gas will be found of such value as greatly to diminish the cost of this 

 process. 



