552 



. KNOWLEDGE • 



[April 28, 1882. 



bell at a distance of 300 miles. The magnets used are very 

 good, and uro claimed to bu capable of sustaining ten times 

 ^eir own weight. 



In the .same series of exhibits is a large switch-board 

 (intendi'd for tclcplione exchange ollices), by means of 

 whicii any one of the lifty subscribers it is constructed to 

 acconnnodate may be put in communication with either of 

 the oth('r subscribers. 



In the "Telegraphs" class there is a tolerably good 

 display of certain forms of apparatus, although none of 

 the high-speed instruments are shown. The British Govern- 

 ment manufacture their own apparatus ; but railway 

 companies, submarine cable companies, and foreign and 

 colonial administrations (all of which, generally speaking, 

 use the Needle, Morse, and other low-speed systems), doubt- 

 less give plenty of employment to makers of such instru- 

 ments as are here exhibited. 



In the class set apart for electro-medical apparatus, 

 Messrs. Blakey A Co. have a very good exhibit, embracing 

 several forms of battery, more especially noted for the 

 fittings. Amongst the apparatus may be noted Messrs. 

 Mottershead 1- Co.'s Leclanche Batteries. They consist of 

 20, 30, or 50 cells. Tliese cells are made of vulcanite, 

 and are all sealed up after being charged, so that none of 

 the liquid can be spilled. Our readers may be aware that 

 the Leclanche Cell contains no acid, and, if only required 

 for a few minutes at a time, it will last for many months — 

 perhaps years. The reason of this is that, whereas in an 

 acid battery, chemical action takes place whether the 

 electrical circuit is complete or not, in such batteries as 

 the one we are considering, no action goes on unless there 

 is a complete electrical circuit. 



The batteries are manufactured in two series, the first 

 being handsomely fitted in mahogany cases, with nickel- 

 plated or gilt accessories, while the second series are fitted 

 up in plain black wood cases. It is asserted that the same 

 cells are used in each series, so that they are equally 

 efiicient. The utility of such an arrangement is obvious, 

 and it is to be hoped that other makers will see their 

 way to following so good an example. 



A little switch (or, as they call it, a current selecter) is 

 fitted to the case, to enable the operator to bring any 

 required number of cells into action, a set of shunts being 

 also provided for cutting oil" the initial cells, and so equal- 

 ising the labour which the various cells are called upon to 

 perform. It is hardly necessary or advisable to enlarge 

 upon the various forms of electrodes exhibited, design <d, 

 as they are, for a multitude of purposes, nor can we now 

 enter into a description of the other apparatus in this 

 collection, but it is recommended that our readers visiting 

 the Palace should inspect it for themselves. 



There are several other exhibitors of electro-medical 

 apparatus ; but grave doubt exists in the minds of elec- 

 tricians, as well as physician.s, as to the utility of a con- 

 siderable proportion of the appliances now before the public, 

 and a great deal remains to be proved before any appre- 

 ciable amount of faith in them can be said to exist. We 

 should have said more about them, but there are many 

 other subjects which demand our consideration — such as 

 secondary batteriis and electro-motors, to one of which we 

 must next direct our attention. 



Reclamation. — A correspondent, with a signature so sinp:ularly 

 business-like that we can only guess tliat his name ends with the 

 letters "an," or "oin," or " nrd," informs us that the information 

 respecting " Accnmuhitive Sinking Fund," at p. 51 1, is taken without 

 acknowledgment from his " Insjall's Foreign Slk (or Tlk) Manual." 

 Wo regret that any correspondent should have failed to mention 

 the source from wliicli information sent to us has been obtained ; 

 but, doubtless, the omission was due to inadvertence. 



iRcbifUjsf. 



THE STARS AND THE EARTH. 



V CHARMING little work. If there is any way in 

 which the human mind can conceive the possibility ot 

 Omniscience, it is the way shown by the author (unknown) 

 of this treatise. He shows that tlie universe encloses 

 the pictures of the past, like an indestructible and in- 

 corruptible record containing the purest and clearest truth. 

 " As sound propagates itself in the air, wave after wave, 

 and the stroke of the Ijell or the roar of the caiuion is 

 heard only by those who stand nearest, in the same moment 

 when the clapper strikes the bell or the powder explodes; 

 l)ut each more distant spectator notes a still greater interval 

 between the light and the sound, until the human ear is no 

 longer able to perceive the sound on account of the distance, 

 — so, according to our ideas, the pictures of every occurrence 

 propagate themselves into the distant ;ether upon the wings 

 of the ray of light. Thus that record which spreads itself 

 out further and further in the universe, by the vibration a{ 

 the light, really and actually exists and is visible ; but to 

 eyes more powerful than those of man." This is the lesson 

 expounded in the first part of this little book. The second 

 still further illustrates this pregnant idea, by showing that 

 a point of view is conceivable from which the universe no 

 longer requires the expansion of time and space in order 

 to exist and to be intelligible to us, and how with such a 

 point of view we can imagine and completely understand 

 the universe as the work of a single Creator. 



CmxKSE Mr.inoD of Maxcfactcrisg Yermiliox. — There aroj 

 three vermilion works in Hong-Kong, the method of manufacture 

 being exactly the same in each. The largest factory consumes 

 about 6,000 ijottles of mercury annually, and it was in this one that ; 

 the following operations were witnessed: — First Step : A large, 

 verj' thin iron pan, containing a weighed quantity (about 14 lb.) of 

 sulphur, is placed over a slow fire, and two-thirds of a bottle ' 

 of mereurj- added. As soon as the sulphur begins to melt, the 

 mixture is vigorously stirred with an iron stirrer until it assumes 

 a black, pulverulent appearance, with some melted sulphur 

 floating on the surface. It is then removed from the fire and 

 the remainder of the bottle of mercury added, the whole being 

 well stirred. A little water is now poured over the mass, which 

 rapidly cools it. The pan is immediately emptied, when it 

 ready for the next batch. The whole operation docs not last mote 

 than ten minutes. The resulting black powder is not a definite 

 sulphide, as uncombined mercury can be seen throughout the whole 

 mass ; besides, the quantity of sulphur used is much in excess of the 

 amount required to form mercuric sulphide. Second Step : The 

 black powder obtained in the first step is placed in a semi-hemi- 

 spherical iron pan, built in with brick, and having a fireplace 

 beneath, covered over with broken pieces of porcelain. These are 

 built up in a loose porous manner, so as to fill another semi-hemi- 

 spherical iron pan, which is then placed over the fixed one and 

 securely luted with clay, a large stone being placed on the top 

 of it, to assist in keeping it in its place. The fire is then 

 lighted and kept up for sixteen hours. The whole is then 

 allowed to cool. When the top pan is removed, the vermilion, 

 together with the greater part of the broken porcelain, is attached 

 to it in a coherent mass, which is easily separated into its compo- 

 nent parts. The surfaces of the vermilion which were attached to 

 the porcelain have a brownish-red and polished appeai-ance, the 

 broken surfaces being somewhat brighter and crystalline. Third 

 Step : The sublimed mass obtained in the second step is pounded in 

 a mortar to a coax'se powder, and then ground with water between 

 two stones, somewhat after the manner ot grinding corn. The 

 resulting semi-fluid mass is transferred to large vats of water, and 

 allowed to settle, the supernatant water removed, and the sediment 

 dried at a gentle heat. When dry it is again powdered, passed 

 through a sieve, and is then tit for the market. — Journal of the 

 Society of Chemical Industry. 



* " The Stars and the Earth : or Thoughts upon Space, Time, and 

 Eternity." (Bailli^re, Tindall & Co., London.) 



