Vol. XXIII. No. 5.] 



POPULAR SCIENCE NEWS. 



7i 



The Largest Railway Station in the World, 

 is the one at Frankfort-on-the-Main. It covers a 

 superficies of 335,916 square feet. Hitherto, the 

 largest stations have been the Saint Pancras at 

 London (166,6^5 square feet), and the Sile-sia station 

 at Berlin (130,000 square feet.) That of P'rankfort 

 is double the size of the first named. 



Inspection of the Interior of Steam-Boilers. 

 — Mr. E. Blass, a German scientist, has used an in- 

 candescent lamp for actual inspection of the inside 

 of boilers under steain. A thick glas.s tube was in- 

 troduced through a stuffing box, a small incandescent 

 lamp was lowered into this, and lighted b_v means of 

 a small battery. Bj this means the whole of the 

 boiler was lighted up, and could l)e inspected 

 through a thick glass plate inserted in the boiler. 



Engraving by Electricity. — A process of en- 

 graving on glass and crystal by electricity has been 

 communicated to the French Academy of Sciences 

 by .M. Plante. The plate to be engraved is covered 

 with a concentrated solution of nitrate of potash, 

 and put in connection with one of the pol!s of the 

 battery, and the design is traced out with a fine 

 platinum point connected to the other pole. The 

 results are said to be of marvelous delicacy. 



A Large Corpor.\tion. — The total miles of 

 wire controlled by the American Bell Telephone 

 Company is 145,732, of which S.ooo are under 

 ground. The total number of employes is 6,132, 

 and the total number of subscribers 158,732. The 

 statement of the treasurer shows that the earnings 

 from all sources, last year, were $3,453,027.70, and 

 expenses $1,242,430.89, leaving the net eurnings 

 $2,210,956.81. The dividends paid during the year. 

 16 per cent, on the capital stock, amounted to 

 $1,568,326. 



Rubber Pavements. — In several cities in Ger- 

 many, notably Berlin and Hamburg, the experiment 

 is being made of a compound for paving purposes, 

 the principal ingredient of which is india-rubber. 

 As lar as heard from, this paving is very satisfactory, 

 although no facts are given as to the cost. The 

 india-rubber combines some elasticity with durabil- 

 ity, is not affected by heat or cold, and in particular 

 does not become slippery when wet, as does asphalt. 

 The roadway over the Goethe bridge in Hanover is 

 also said to have been paved with this compound, 

 and to have been found very satisfactory. 



Fire and Water-proof Paper. — Among the re- 

 cent German patents, there is one for an article 

 which, if it turns out to be all that is claimed for it, 

 will be immensely valuable. It is for a fire and 

 water-proof paper, and was granted to M. Ladewigg. 

 The process, in brief, is as follows : Twenty-five 

 parts of asbestos are mixed with from twenty-five 

 to thirty parts of aluminum sulphate, moistened 

 with a solution of zinc chloride, and well washed 

 in running water. The pulp is then treated with a 

 solution of one part of resin soap and eight to ten 

 parts of pure aluminum sulphate, after which it is 

 made into paper exactly as rag pulp is. 



Novel Lighting System for Paris. — A F"rench 

 electrician, M. G. A. Tabourin, has invented a 

 novel method of lighting the streets, which will do 

 away with underground mains, and permit the rapid 

 extension of electric light throughout Paris, without 

 interfering with the gas companies. In this system, 

 each gas lamp is to be furnished at its base with a 

 small rotary gas engine, ten inches in diameter, 

 and a small dynamo, and these small installations 

 are to supply lamps on the top of the lamp posts, 

 thus burning gas at the bottom and producing 

 electric light at the top of each post. The inventor 

 oflfers to run at his own cost for several days, oppo- 

 site the Theatre Francais, one of these electric lights 

 on his new system. 



J^oiQe, Barni, aijd Gardeij. 



THE REASON WHY. 



Vegetabi.e.s and meats are sealed up in air- 

 tight vessels to preserve them, so that the 

 bacteria, or minute organisms which are al- 

 ways present in the air, and which would 

 cause them to putrefy and decay, are thus 

 excluded. The jars are heated before tiiey are 

 finally sealed, so as to destroy any bacteria 

 that may already be present in the food. 



Blueing is added to the water in which 

 linen is washed, to neutralize the dull yellow 

 tint which clean linen always possesses. Blue 

 and yellow are complementarv colors — that 

 is, when mixed together they make white — so 

 that the peculiar shade of yellow, which is 

 common to all intensely white bodies, and 

 which may be — partially, at least, — an optical 

 illusion, is neutralized by the blue. Paper, 

 sugar, starch, and many other substances are 

 treated in the same way. 



Baking powders are mixtures of chemicals 

 which, when moistened, liberate carbonic 

 acid gas. They are added to the Hour used 

 in bread-making, so that the gas, as it escapes, 

 may puft" up the dough, rendering it spong>- 

 and light. Yeast serves the same piupose by 

 causing a fermentation in the flour, which 

 also develops carbonic acid gas. 



The experienced housekeeper is careful 

 not to boil preserves and jellies too long after 

 the sugar has been added, because the acids 

 in the fruits may cause the sugar to "invert," 

 or split up into two other forms of sugar, 

 neither of which possesses much sweetening 

 power. Neither will she boil jellies made 

 from gelatine too long, or a chemical change 

 will take place, and the gelatine lose its 

 power of '"setting," or gelatinizing. 



Dry wood gives a hotter fire, and is more 

 economical to burn than green wood, because 

 the latter contains more water, and a large 

 part of the heat of the fire is wasted in con- 

 verting it into steam, which passes off up the 

 chimney, thus carrying the heat into the outer 

 air, where it is wasted. 



Soap-suds are better than water for washing 

 purposes, because the soap forms a chemical 

 combination with the greasy matters present, 

 and renders them soluble in water. Without 

 this help, the water could not dissolve them. 



Hard water is wasteful of soap, because it 

 contains lime salts, which form an in.soIuble 

 compound with the soap, thus rendering a 

 part of it useless. 



Oil collects on the outside of lamps, because 

 of the capillary attraction of the wick, which 

 draws it up from the inside, and allovvs it to 

 run over the top of the tube in which the 

 wick is placed. To prevent this, turn the 

 wick down below the top of the wick-tube 

 when the lamp is not in use. 



Cake will "fall" while baking, if the oven 

 is suddenly cooled, because the steam and 



gases which puft' it up and make it spongy, 

 are condensed, and escape, before the albu- 

 men or egg in the cake has become coagulated 

 and hard. Albimien, or white of egg, is a 

 liquid at ordinary temperatures, but, at tlie 

 heat of the baking oven, becomes a firm and 

 hard solid, giving stiffness and body to the 

 cake which contains it. 



Wet clothing hung out on the line will dry 

 when the temperature is below freezing, 

 because ice evaporates into the air, just as 

 water does, although more slowly, without 

 passing tiirough the intermediate liquid state. 



The "fur" on the inside of the tea-kettle 

 comes from the salts of lime in the water. 

 They are held in solution by the carbonic acid 

 gas present, but when this is driven off by 

 boiling, thev are precipitated on the sides of 

 kettle. Scale in steam-boilers is due to the 

 same cause. 



Cider is turned into vinegar upon exposure 

 to the air, by the oxygen gas in the air, which 

 unites with, or oxidizes, the alcohol, changing 

 it intf) acetic acid, of which vinegar is only a 

 weak solution. 



Pitkles are colored green by boiling in a 

 copper kettle, because the vinegar unites with 

 the copper, forming a green-colored salt, sim- 

 ilar to verdigris. As this coloring matter is 

 unwhole.some and poisonous, the practice is 

 not one to be recommended. 



Tea, coffee, and .spices lose their strength 

 when kept in open boxes, because they con- 

 tain volatile flavoring oils, which gradually 

 evaporate when exposed to the air. Always 

 keep them in tight cans or bottles. 



Soot falls down the chimney before a storm, 

 because the air at that time contains more 

 moisture. Soot is hygroscopic — that is, it 

 absorbs the moisture from the air, — and, be- 

 coming heavier, detaches itself from the sides 

 of the chimney. 



Butter becomes rancid, because of the for- 

 mation in it of butyric acid, by a peculiar 

 fermentation. As this ill-smelling acid is 

 volatile, and is driven off" at high temperature, 

 rancid butter may sometimes he used for 

 cooking purposes without offence. 



Syrup and molasses will sometimes begin 

 to ferment, or "work," in exactly the same 

 way that bread does while rising. It can be 

 stopped by boiling them, which kills the 

 yeast plant upon which the fermentation 

 depends. 



Carpets and upholstery fade when exposed 

 to the sun, because of the actinic or chemical 

 power of the sun's rays, which decompose 

 the dye-stufTs. The process is closely analo- 

 gous to that which occurs in the taking of 

 photographs. 



Glassware cracks when placed in hot 

 water, because, being a poor conductor of 

 heat, the outside becomes hot, and expands, 

 while the interior is still cool. The strain 

 resulting from this unequal expansion causes 



