April 27, 1S8S.] 



SCIENTIFIC NEWS. 



387 



I have controverted this conclusion (see " Science in 

 Short Chapters," page 88), not on any theoretical grounds, 

 but as a simple matter of fact, which anybody may 

 rectify by repeating my observations at the Aachensee 

 in the Tyrol, and in the Norwegian ijords, where 

 thousands of trees are annually swept down from the 

 steep slopes on which they grow, with soil still adhering 

 to their roots. This soil holds the floating trunks for a 

 while in upright position, until sufficiently soaked to 

 sink to the bottom of the lake or fjord, still with roots 

 downwards, in which position they become either 

 embedded in the deposit from the turbid inflowing 

 waters of the head river, or if in the outer clear water of 

 the lake or fjord, are in the course of centuries 

 associated with other trees in sufficient quantity to 

 become rotted down into coal-seam material. 



large hollow caisson moved by means of rollers running 

 on a tramway laid on a bridge placed above the gate 

 when the lock is closed. When it is to be opened the 

 gate is run into a side chamber made for its reception in 

 the bank of the canal, as shown in the accompanying 

 illustration, and the bridge is then swung round on a 

 pivot so as to leave the canal passage clear. The lock 

 gate is formed of numerous water-tight compartments, 

 independent of each other, and it is possible to introduce 

 into them at pleasure either water to equalise the pres- 

 sure, or compressed air to allow of the compartments 

 being examined and repaired. 



As the gate has a slight lateral movement, it can- 

 not remain jammed against its supports, an acci- 

 dent which frequently occurs in similar systems, and 

 even in gates made in pairs. Further, as the sliding- 





THE PANAMA CANAL LOCKS. 



A CCORDING to La Nature, the projected opening of 

 -^~^ the Panama Canal in 1890, depends on the adop- 

 tion of a higher level in the Cordillera, and on the use 

 of locks with a depth fiom 26 to 36 feet of water as pro- 

 posed by M. Eiffel. These locks will be about 590 feet 

 in length, and 58 feet in width. 



For such pressures and for locks which have to be 

 opened and shut frequently, the ordinary irrangement of 

 lock gates in pairs is not suited. Hence M. Eiffel, with the 

 concurrence of M. Bunau-Varilla, proposed a single lock 

 gate to run on rollers as used by M. Kinipple since 1874 

 for the docks at'Greenock and elsewhere. Instead, there- 

 fore, of the lock being closed by a pair of gates opening 

 and turning upon hinges hke ordinary gates, the canal 

 will be closed by a single shding gate which moves verti- 

 cally to the line of the canal. 



This gate is a rectangular structure of iron forming a 



gate is buoyant, it does not weigh heavily upon its bear- 

 ings and impose any severe strain upon them. A very 

 little power is sufficient to open and close the lock 

 quickly. In the opinion of competent engineers, this 

 system is considered the best for locks having a great 

 fall of water. The gates are, of course, only moved when 

 the level of the water is the same on each side. Provi- 

 sion must, therefore, be made for passing from one side 

 to the other, the enormous quantity of 1,400,000 c. ft. 

 of water in fifteen minutes at the utmost, and this 

 without undermining the lock sills, and without pro- 

 ducing such a movement in the water as would drive 

 vessels against the banks and cause them to come in col- 

 lision. To this end M. Eiffel causes the water to flow in 

 through a series of vertical pipes on each side of the lock, 

 insteadof escaping laterally through a few large openings. 

 We are indebted to our contemporary. La Nature, for 

 the illustration we give, and for the information upon 

 which our description is based. 



