MECHANICAL IMPROVEMENTS. 



497 



55.9 miles) an hour, and other speeds, and 

 under differing brake pressure, and other vary- 

 ing conditions. Under a brake pressure of 

 50 per cent, of the tire pressure of the wheels, 

 on a declining grade of 1 in 125, at the speed 

 of 46.6 miles an hour, the loss by momentum in 

 133 metres (437 feet) was, with the different 

 forms, as follows : With the Westinghouse, 

 17.82 per cent. ; Heberlein, 13.65 per cent. ; 

 Steel, 12.26 per cent. ; Smith, 11 per cent. At 

 a speed of 55.9 miles per hour, distance 656 

 feet on a level, the retarding effect was regis- 

 tered : "Westinghouse, 25.74 per cent. ; Steel, 

 21.93 per cent. ; -Smith, 20.4 per cent. ; Heber- 

 lein, 19.96 per cent. At 46.6 miles an hour, 

 and 87 per cent, brake pressure, the results 

 were : Westinghouse, 59.43 per cent. ; Steel, 

 40.85 per cent. ; Heberlein, 39.67 per cent. At 

 a speed of 46.6 miles on a level, after a dis- 

 tance of 984 feet, brake pressure 50 per cent., 

 the results were as follows : Westinghouse, 

 54.70 per cent. ; Smith, 41.89 ; Heberlein, 

 39.13; Steel, 35.18. 



The wire tramway, invented by Mr. Hodg- 

 son, is a very useful contrivance for transport- 

 ing light goods over short distances, which is 

 coming into general use in England. An im- 

 provement, consisting of a peculiar kind of 

 grip, which prevents the load from slipping on 

 the rope when ascending or descending a grade, 

 allows of the tramway being worked on in- 

 clines as steep as 1 in 3. It has been suc- 

 cessfully applied to the loading and unload- 

 ing of vessels whose anchorage is too distant 

 from shore to admit of the construction of a 

 pier. The terminus is connected with a group 

 of piles placed in deep water; the wooden 

 posts which support the ropes are driven at 

 distances of 60 yards apart. The power which 

 works the carrying ropes can be transmitted 

 over them at the same time, so as to work the 

 cranes at the terminus which are used in ship- 

 ping or unshipping the cargo. 



Laing's overhead sew ing-machine is an Eng- 

 lish invention, by which the ordinary stitch of 

 hand-sewing is reproduced, the thread passing 

 through and around the edges of the seam. 

 The needle is of spiral shape, passing three 

 times around a central spindle ; the thread is 

 caught by a hook at the latter end of the 

 needle, and by a special apparatus, when the 

 thread on a spool is exhausted, another spool 

 is automatically brought in place, and the 

 needle threaded without any stoppage of the 

 work. The stitch is precisely identical with 

 hand-sewing, but beautifully and perfectly 

 regular. The fabric is fed by a spiked chain 

 with a velocity which can be regulated at pleas- 

 ure ; the greater the velocity the longer being 

 'the stitch, the elasticity of the needle allowing 

 it to elongate. The length of feed can be 

 regulated, and the depth of the edging of the 

 seam-is determined by a guard on the feeding- 

 plates. 



An English inventor, George Jenkins, has 

 planned a system of hydraulic machinery for 

 VOL. xvii. 32 A 



lifting ships up inclined slips, by which the ac- 

 tion is consecutive, and the injurious inter- 

 mittent arrests accompanying the strokes of the 

 ram in the ordinary apparatus are avoided. It 

 consists of two pairs of hydraulic cylinders, 

 one before the other ; the rams of each pair are 

 connected with a crosshead, through which the 

 traction links pass; two posts are placed on 

 each crosshead, connected above by a horizontal 

 bar, in the centre of which is keyed a double 

 segment ; at one end of the horizontal shaft it 

 is worked by a hand-lever ; one arm of the seg- 

 ment has a weight, and the other an iron stop- 

 per attached to a chain, which fits, when the 

 segment is lowered, between pairs of links 

 placed at proper intervals in the traction rod. 

 When the stopper of one pair of cylinders is 

 lowered into position between a pair of links, 

 and against the crosshead, the rams are set in 

 motion, and before the stroke is completed the 

 stopper connected with the other pair of rams 

 is inserted between the next pair of links, the 

 weight drawing out the first stopper as the 

 force of the second pair of rams carries the 

 traction rod farther and relieves the strain on 

 the first stopper. When the second pair of 

 rams have nearly completed their strokes, the 

 first stopper is again lowered, and the first pair 

 of rams, which have been in the mean time 

 run back, carry the cradle up the distance of 

 another interval between the links in the trac- 

 tion rod. 



The Berlin pneumatic postal dispatch sys- 

 tem comprises 15 stations, and 26 kilometres 

 of tubing, which is laid about one metre below 

 the surface of the ground. The pipes are of 

 wrought-iron, with a diameter of 65 millime- 

 tres. Letters and cards to be sent are to have 

 a fixed size; they are inclosed in iron boxes 

 made to hold 20 each ; 10 or 15 boxes form a 

 train, with one behind with a leather ruffle to 

 fill the tube and prevent the passage of any air. 

 Exhausting machines and apparatus are placed 

 at four of the stations. Both condensed and 

 rarefied air, or a combination of the two, are 

 employed in propelling the load. Steam en- 

 gines of 12-horse power, two at each of the 

 four stations, are required to condense and 

 rarefy the air, the condensing and rarefying ap- 

 paratus being connected with large reservoirs. 

 The condensed air has a tension of three at- 

 mospheres ; the rarefied air of 85 millimetres 

 of mercury. The reservoirs are surrounded 

 by water to cool the condensed air, which is 

 heated by the operation to a temperature of 

 45 0. The velocity with which the mes- 

 sages are transmitted averages 1,000 metres per 

 minute; the loads are dispatched at intervals 

 of 15 minutes. The system is divided into two 

 circuits, each of which is traversed in 20 min- 

 utes, including stoppages. The estimated cost 

 of the entire work is a million and a quarter 

 marks. 



Jablochkoff, whose electrical candle already 

 assumes a high position among artificial illumi- 

 nators, has made important improvements in his 



