198 MANGANATES 



but all the other man-engines are worked by the ordinary Cornish steam-engine, that 

 is, with a cylinder vertical and balanced ; and always double-acting. The outer end 

 of the beam of the machine is attached by a sweep-rod to two small wheels which are 

 situated on the shaft ; these drive two larger wheels, so that the engine makes several 

 strokes to one revolution of the wheels. In some of the mines the engine, besides 

 giving motion to the man-engine, is used for crushing the ores and performing 

 other work, while in others it is merely employed for raising and lowering the 

 miners. The rods are generally about 7 or 8 inches square, slightly decreasing in 

 size as they descend. When there are two rods the steps are so placed that there 

 is a distance of about 6 inches between them when the man passes from one to the 

 other. The weight of the rod is counterbalanced sometimes by levers and sometimes 

 by balance-bobs attached to it in different levels. The greatest object gained in the 

 use of levers is a considerable saving in expense, both in the materials of which 

 they are made, and in the size of the piece of ground that must be excavated to 

 receive the balance-bobs. There are twelve feet of space between the step on the rod, 

 and 4 feet above each step are round bars of iron fixed vertically into the rod, to serve 

 as hand-holds, and maintain the miner in his position on the step with perfect safety. 

 In case of accident happening to any part of the machinery, there are catches placed 

 at every few fathoms, so that the fall cannot be great. 



The man-engine with a single rod is generally used in Cornwall, because it possesses 

 eo many advantages over that with two : the expense of erection is much less, it 

 enables the miner to mount and descend in as short a space of time, and the number 

 who can do so per minute is doubled ; the work performed by the machine is also 

 increased. There are signals connected with the man-engine, by which the miner can 

 communicate with the surface from every platform. 



The usual speed of the engine is 15 strokes per minute, by which each rod makes 

 3 strokes during that time. Therefore, the rate at which it travels is 12 fathoms 

 per minute ascending and descending : this speed enables a miner to travel in 24 

 minutes a space that he would otherwise take 60 minutes to perform. In case of 

 any accident happening to the man-engine, there are always ladders placed by the 

 side of it ; sometimes they only go from platform to platform ; in other mines there 

 are bars nailed on the rod, so that the miner can climb on them until he regains the 

 principal ladders. 



The man-engine possesses almost innumerable advantages over the ladders ; the 

 greatest is the immense saving of fatigue to the miner. "When there are only ladders 

 in a mine, he sometimes takes an hour or more to reach the place where he is working, 

 and then only with immense bodily exertion ; on a man-engine he can reach the same 

 place in about a third of the time, and as free from fatigue and ready for hard work 

 as when he started from the surface. Even those who have never been in a mine 

 cannot but appreciate the great blessing this simple invention is to the miners, if 

 they have only seen the exhausted state in which they reach the surface after having 

 ascended by ladders from any great depth. At first it was feared the man-engine 

 might be dangerous, that the speed at which it worked would not allow time for the 

 men to step from one platform to another, but after one or two trials it was found that 

 no fears need be entertained on that account, and it was pronounced by the miners as 

 perfectly safe as ladders. 



In 1845 M. Warocque constructed similar machines in Belgium. These have been 

 described in the Revue Scicntifique et Industrielle, under the several denominations 

 of ' Fahrkunst,' ' Man- Engine,' ' Warocquiere,' ' Machine d'Ascension,' and ' Echelles 

 Mobiles.' The first application was made, as we have already said, by M. Warocque 

 at the pit of St. Nicholas, belonging to the colliery of Mariemont, to a depth of 220 

 metres about 240 yards. A full account of these machines will be found in the 

 Annales deft Travaux publics, tome v., p. 79, by M. Delvaux de Fenffe ; in the 

 Traite d? Exploitation by M. Combes ; Notice sur les Appareils de Translation des 

 Mineurs dans les Pwits, by M. A. De Vaux ; also in the Annales dcs Travaux publics 

 de Belgique ; and by M. Moissenet in the Annales des Mines. 



MANG-ANATES ; PERMANGANATES ; COWDY'S FLUID. Dr. 

 Hofmann, in his report on the chemical products of the Exhibition of 1862, has the 

 following excellent remarks on soluble saline oxidising disinfectants. Of this variety 

 of oxidising disinfectants the alkaline manganates and permanganates are the best 

 examples ; and in this cursory sketch, attention may be confined to these as types of 

 their class. 



Alkaline Manganates and Permanganates. Chemists have long known and turned 

 to account, in laboratory operations, the powerful oxidising action of the salts of 

 permanganic acid. The rapidity and definiteness of their action, and the marked 

 change of colour by which their loss of oxygen is attended, renders these compounds 

 invaluable as instruments of analytical researches. And the same properties, coupled 



