1842.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



277 



vertical glass tube, exhibiting the weight of water witliin. To this tube 

 there was attached a moveable scale, the zero of which being placed on a 

 level with the point at which the water stood when the vessel was at rest, 

 the rise of the water in the tube when the vessel was set in motion exhibited 

 the velocity at which the vessel was passing through the water. With the 

 view of testing the accuracy of this invention, he had tried it repeatedly 

 over a distance of 15 miles, measured trigonometrically. He had also com- 

 pared it witli the best logs, and was perfectly satisfied of its accuracy. From 

 these experiments he had constructed a scale, which he exhibited, and of 

 which the following is a copy ; the first column exhibiting the speed in miles 

 per hour, and the second the height of the water in the tube above the zero 

 line expressed in feet and decimal parts : — 



Miles per hour. Feet on the scale. 



15 7-5625 



14 6-5880 



13 5-6800 



12 4-84 



11 4-067 



10 3-36 



9 2-722 



8 2-151 



7 1-647 



6 1-21 



5 0-84 



4 0-537 



3 0-3025 



2 0-134 



1 0-0336 



A NEW SELF-ACTING Weir AND ScoDRiNG Si.uicE, by Mr. Batcman. 



Mr. Bateman observed that the great objections to fixed weirs and dams 

 were, that by causing a partial stagnation in the water above them, they 

 allowed the bed of the stream to be silted up by the deposition of mud, 

 gravel, &c., whereas the proposed weir would adjust itself to the various 

 changes in the condition of the stream, and prevent any filling up of the 

 channel by making the stream clear itself. Mr. Bateman's weir^is composed 

 of two leaves turning horizontally on pivots, which are placed below the 

 centres of the leaves, so that the upper portions of them shall be of much 

 greater area than the lower. The upper leaf is also far larger than the 

 lower, and turns in the direction of the stream ; while the lower leaf turns 

 against the stream, and overlaps the bottom edge of the upper leaf, and is 

 forced against it by the pressure of the water. The comparative area of the 

 leaves and position of the pivots is so arranged, that in ordinary states of 

 the stream the tendency of the current to turn over the top leaf is counter- 

 balanced by the pressure of the water against the overlap of the bottom one, 

 the counteracting pressures keeping the weir vertical and the leaves closed! 

 the water flowing as usual through a notch in the upper leaf. But when the 

 water rises above the usual level, the pressure above, from greater surface 

 and leverage, overcomes the resistance below, and the top leaf turns over, 

 pushing back the lower leaf, and thereby offering the least possible obstruction 

 to the water, and giving a passage at the very bottom of the stream to the 

 gravel or mud. 



The following diagrams will explain the construction of the weir : — 



In answer to questions and objections, Mr. Bateman explained how diffi- 

 culties, arising from trees floating down, the complete turning over of the 

 leaves, &c., might be obviated by suitable stops, grating, &c.— Sir J. Robison 

 observed, that the Rotterdam Canal had weirs on a similar principle ; but 

 Mr. Bateman explained that those weirs turned vertically on their axis. 

 Mr. Vignoles stated, that from the cheapness and apparent advantages of 

 this weir, he hoped it would be brought under the consideration of the Com- 

 missioners of the Shannon navigation, and recommended for trial on that 

 river, to which it appeared pecuHarly applicable. 



Mr. Bateman, in obviating some difficulties suggested, explained that, in 

 a weir 20 ft. long and 5 ft. deep, which his drawings and model might be 

 supposed to represent, the sum of the closing pressures would be 795C lb., 

 and the sum of the opening pressures would be 7669 lb., the pivots being so 

 placed as- to give the areas of leaves above and below the lines of their axes 

 the ratio of 2 to 1. The leaves would consequentlv be kept close by a force 

 equal to the difference between these pressures;" that is 287 lb. As (he 

 water rises these conditions would, however, be changed. Supposing the 

 water to rise one foot, the additional pressure would be 12001b., of which 

 800 lb. would be exerted in opening, and 400 lb. in closing the leaves ; and 

 the result would be that the sum of the opening pressures would exceed that 

 of the closing by 100 lb. The leaves would consequently be opened. He 

 also explained that the sills against which the gates arc made to close, might 



be so regulated as to discharge the greatest flood o, water without allowing 

 the leaves to open more than a moderate quantity; but, if thought necessary, 

 the gates ought to he allowed to assume a position perfectly horizontal in 

 cases of high floods, and thereby oppose the least possible resistance to the 

 passage of the water. The sluice might also be protected from being choked 

 with trees and brushwood floating down the stream, by means of a grating. 



Mr. Liddell read a paper on Ventilalion, on a met/tod proposed by Mr. 

 Fleming, of Glasgow. It had been tried in a large building occupied by a 

 number of poor persons, each family having a room. From the unclean and 

 intemperate habits of the inmates, and their number (about 500), the house 

 was very unhealthy, and many deaths from contagious diseases took place. 

 In the plan adopted, the galleries were traversed by pipes of nine inches 

 diameter, which united in a vertical pipe of large dimensions communicating 

 with a lofty engine-house chimney ; and small pipes of one inch diameter, 

 at the top of each room, communicated with the pipes in the gallery. This 

 plan had also been tried in the Glasgow Fever Hospital, in which the beds 

 for fever patients, &c. were fitted up with the tubes for carrying away 

 noxious effluvia. ,V similar plan for the ventilation of ships and steamers 

 had been introduced by Dr. Reid, by leading tubes from the berths into a 

 stove on deck, or, in steamers, into the chimney. Mr. Liddell stated that 

 the expense fur a house of 60,000 cubic feet was only 40 lb. of coal in 

 twenty-four hours. 



Sir J. Robison remarked, that from his experience the plan of Mr. Fleming, 

 as far as regarded the size of the pipes, was inadequate. 



ON THE ACTION OF LIGHTNING CONDUCTORS. 



At the meeting of the Electrical Society on Tuesday evening, 19th July, 

 a paper on this subject by Mr. Charles Walker, the Secretary, was read. 

 The author entered into a very close investigation of the most important ex- 

 periments that have been adduced in illustration of the nature "of these in- 

 struments ; and stated that discharges of Leyden batteries have been very 

 generally selected as representatives of lightning flashes. He then showed 

 the great difference between the visible character of the two flashes, and ana- 

 lyzed the cause on which each depends ; demonstrating that the only case in 

 which the resemblance is in any degree to be traced, is when a Levden dis- 

 charge fractures the glass, and passes directly between the coatings ; and 

 that in all other cases the said discharge is the result of two forces acting 

 counter to each other. Thus he reaches his first conclusion, that the dis- 

 charge of a Leyden jar does not resemble a flash of lightning; and therefore 

 that Leyden jars should not be employed in these experiments. He then 

 said that many points on which philosophers of the present day diflVr, are in 

 connexion with the results of the Leyden experiments ; and hence, if it can 

 be shown that these experiments ought to be excluded, the at present com- 

 plicated inquiry will be much simplified. He proceeded to trace the close 

 resemblance between the discharge of a prime conductor and a cloud, illus- 

 trating his opinion by the aid of the magnificent machine belonging to the 

 Polytechnic Institution ; and showed that experiments with this conductor 

 are in all essential points legitimate. He then described an extensive series 

 of experiments to prove that a wire on which sparks are thrown from the 

 prime conductor represents a lightning-rod ; and then that sparks will pass 

 from such a wire, and therefore from a lightning-rod, to vicinal conducting 

 bodies. This last position was illustrated in a general manner by an assist- 

 ant holding in his hand a glass rod surmounted by a brass ball ; the ball was 

 connected by stout wire with the gas-burners of the room, and thus when 

 sparks were thrown on it from the conductor the electricity passed into a 

 good discharging train to the earth. Now, while this took place, the appli- 

 cation of a piece of metal to any part of the wire produced a spark ; and not 

 only so, but the same could be obtained from any of the gas-burners in any 

 part of the room ; and even when the writer descended into the workshops, 

 two stories below the machine, sparks could be obtained from the burners 

 there, which v«re indeed very much out of the direct line of circuit, so great 

 is the desire of the electric current to use a wide path. This is the source 

 of danger alluded to in the paper on Brixton church, reported in the last 

 Journal. However, as the wires |in this, as in several other similar experi- 

 ments, were not directly between the conductor and the earth, the follow- 

 ing arrangement was made, which answers every condition, and the general 

 result of which proves that tlie wires above described do act as lightning- 

 rods. Attached to the prime conductor of the machine was a thick brass 

 rod, terminating in a five-inch ball ; immediately beneath this was erected 

 a similar rod surmounted by a ball. This rod was screwed into a small brass 

 disc on the floor, and was considered a perfect representation of a lightning- 

 rod, when sparks or 'flashes were passed into it. Near this a shorter and 

 smaller rod (also terminating in a ball) was held ; when the end of this rod 

 touched the brass disc, no sparks passed between the two, when it did not 

 touch, sparks passed in abundance. Much of the value of the inquiry was 

 shown to depend on this experiment. If the former state of things repre- 

 sents what occurs in nature, there is no danger of a lateral spark ; but if the 

 latter, the danger is great. That metallic contact in this experiment pre- 

 vented the appearance of sparks is an experimental proof of the safety result, 

 ing from the metallic coonf-nions formerly recommended. These latter re 



2Q 



