TRANSACTIONS 01' THE SECTIONS. 239 



petition, necessarily insure inspection, inasmuch as the number of explosions being 

 one in 2000 boilers per annum, it follows that the net cost of insurance is only one 

 shilling- for every £100, whicb. must evidently be inadequate for any description 

 of inspection by way of prevention. Insurance, therefore, as previously pointed 

 out, is cheap, while adequate inspection is costly ; so that inspection is opposed to 

 dividend, for which joint-stock companies are clearly established. Some correc- 

 tive, therefore, is plainly necessary, and this it is thought would in some measure 

 be found by the establishment of a tixed substantial penalty in the event of every 

 explosion, irrespective of the amount of damage done. Also the imposition of a 

 penalty on every inspection-association or insurance company failing to prevent 

 the explosion of a boiler under their care, might have a most wholesome tendency, 

 this penalty being ecjual and in addition to the one imposed on the owner, and; in 

 like manner, devoted to the support of the compensation fund *. 



In conclusion, although entire assent cannot be accorded to the Pai'Uamentary 

 Report, yet it is most cordially wished that every success may attend the adoption 

 of the measures recommended therein, and that they may result in preventing 

 many explosions, and in diminishing the lamentable loss of life at present result- 

 ing from the constant recurrence of these catastrophes. 



On Designing Pointed Eoofs. By Thomas Gilloit. 



Description of a Salmon-ladder meant to suit the varying levels of a LaJce or 

 Reservoir. By James Leslie, M.I. G.E. (Commumcatcd by Alex. Leslie.) 



So long as the reservoir or lake is full and overflowing the fish may ascend the 

 waste weir if not too steep, and if otherwise properly constructed and furnished; 

 where necessary, with a salmon-ladder ; but whenever the water ceases to overflow 

 the waste weir, the means for the ascent of the fish are generally cut off. 



The sluices at the outlet of a lake used as a reservoir are in general (though. 

 there may be exceptions to the rule) placed at or near the lowest level of the 

 outlet; and the velocity of the current through them is consequently, in most 

 cases, so great that no fish can swim against it until the surface of the water be 

 run down so low as to be near the level of the outlet, and the velocity be thereby 

 reduced ; and in that latter case the power to ascend into the lake is of no great 

 value, as the salmon have little or no disposition to run during droughts. 



This design consists of a series of sluices placed side by side at different levels, 

 each sluice opening by being lowered instead of by being raised, as is the general 

 mode, and each commencing with the salmon-ladder, which passes along in front 

 of the sluices, and is composed of alternate pools and falls. In this design it 

 is contemplated that on all occasions the whole outflow required to run down 

 the stream should be through mily one sluice at a time, and over the top of 

 that sluice, which would open by lowering, and shut by being raised, except in 

 extreme floods, when, for the sake of keeping down the level of the lake, so as to 

 avoid flooding the adjoining lands, or for any other similar reason, it may be neces- 

 saiy to provide a lower outlet, or the means for a more rapid discharge for the 

 water. 



Assuming an instance of a lake with a rise and fall on the surface of 12 feet, 

 and that it is full, or just up to the level of the waste weir; the uppermost sluice 

 of the series is opened so that the water may How over it to the depth of, say, 9 or 

 12 inches, which depth we mav assume to be necessary to give the statutory com- 

 pensation. The water will then run down the ladder, which is composed of a 

 series of pools formed by stops reaching quite across from wall to wall, the fall 

 from surface to surface of those steps being 18 inches, and the depth of the pools 

 not less than 3 feet. A fish may then easily leap over the successive falls from 

 the lowest to the highest, after which they must take the last leap over the outlet 

 sluice into the lake, that last leap being'at first like all the others, 18 incheS; but 



* The exemption described above in favour of steam-users should also apply under 

 similar circumstances to Inspection Asaociations or Insurance Companies. 



