Che ^ojjular Science j^ttps 



AND 



BOSTON JOURNAL OF CHEMISTRY. 



Volume XXIII. 



BOSTON, OCTOBER, 1889. 



NUMHKIt lO. 



CONTENTS. 



Familiar Science. — The Hydraulic Top . . 145 



The Weight of Gases . '. 145 



The Limits of Vision 146 



Modern Archa;ological Discoveries . . . 146 



Algebraic Puzzles 147 



The Toronto Meeting of the American Asso- 

 ciation for the Advancement of Science . 14S 



Practical Chkmistry and the Art.s. — A 



Mediitval Railwav 149 



The Use of Bisulphide of Carbon in Boilers 149 



A New Photographic Chemical 15" 



Railroad Notes i.S" 



Practical Recipes 150 



Home, Farm, and Garden. — The Nitrogen 



Bacteria 151 



Coco, Cacao, and Coca 151 



Horticultural Hints 152 



Editorial. — Paris Letter 154 



Meteorology for August, 1889, with Review 



of the Summer 154 



Astronomical Phenomena for October, 1889 155 



Qiiestions and Answers 155 



Literary Notes 155 



Medicine and Pharmacy. — Some Facts Con- 

 cerning Anifsthetics 15^ 



Monthly Summary of Medical Progress . . 156 

 Condensed Milk, with Reference to Previous 



Skimming ISS 



The Elixir of Life 158 



Pharmaceutical Memoranda 15S 



Publishers' Column 15S 



Banjiliar Science. 



THE HYDRAULIC TOP. 



The ingeniou.s little toy represented in the 

 engraving, outwardly resembles an ordinary 

 top, furnished with a cup-shaped holder (B), 

 on which it is placed while spinning. The 

 holder is covered with rubber on the bottom, 

 to prevent the motion of the top from displac- 

 ing it. When the holder is placed in a deep 

 dish filled with water, and the top set spin- 

 ning upon it, a fine stream of water flows 

 through the top, and is thrown out above, 

 like a miniature fountain, to a height of two 

 or three feet. 



The simple interior construction of the top 

 is shown in the illustration. The body (A) 

 is hollow, forming a reservoir (R), with an 

 opening at the bottom, which dips beneath 

 the surface of the water. The central axis, 

 or spindle, around which the top revolves, is 

 hollow and provided with a horizontal tube 

 (C), extending nearly to the side of the res- 

 ervoir. Attached to the inside of the reser- 



voir, and revolving with it, are two little 

 metal wings, or propeller-blades, (not shown 

 in the engraving), which, by their motion, 

 force the air in the reservoir through the 

 tubes (C, D), creating a partial vacuum, and 



drawing the water in the di.sh up into the top 



and through the tubes. This hydraulic top, 



which first appeared at the Paris Exposition, 



is, in fact, a water-pump on a small .scale, 



and is an instructive and amusing scientific 



toy. 



— ..«4 



THE WEIGHT OF GASES. 



It is hard to realize that gases, like the air 

 aroimd us, or those produced by the chemist, 

 really posi^ess weight, the same as the more 

 palpable solids and liquids. A gas is such a 

 subtle, mobile body that it makes very little 

 impression upon our senses, and special 

 arrangements are necessary to show that 

 gases and vapors are really heavy bodies, 

 like all other forms of matter. 



Hydrogen, the lightest of all gases, is not 

 easily prepared, and is not well suited for 

 experiments upon density, especially as it 

 possesses such a high diflusibility that it 

 mixes at once with the surrounding air. 

 Carbonic dioxide, or carbonic acid gas, is, 

 however, a very heavy gas, and difluses into 



the sinnoimding air slowly, so that, with a 

 little practice, it may readil)' be poured from 

 one vessel to another like water, and, by 

 reason of its tliflerent refractive power, the 

 stream of gas may even be visible to the eye 

 when phiced between it and the light. 



The two accompanying engravings are 

 from the Scientific American^ and illustrate 

 two simple forms of apparatus for showing 

 t!ie weight of the gas. In Fig. i a simple 

 balance constructed of wire is shown, to one 

 end of which a large paper ])ox is suspL-nded. 

 Weights are placed in the opposite pan until 

 the whole just balances, and then, if a bottle 

 full of carbonic dioxide is inverted over it, 

 the heavy gas will displace the air and the 

 box will fall, showing that a heavier substance 

 has been placed in it. In Fig. 2 a tittle 

 wheel of cardboard is shown, which can be 

 made to revolve like an overshot water-wheel 

 by pouring a stream of the invisible gas into 

 the paper cones as they move around. 



Another experiment to show the weight of 

 the gas, is to place a soap bubble in a jar 

 partly filletl with it. The bubble will rest 

 upon the upper surface of the gas like a bal- 

 loon floating in the air: or the smoke of a 



Fig. I. 



cigar, or piece of smouldering paper will act 

 in the same way. 



Carbonic dioxide extinguishes flame, not 

 by any inherent power in itself, but by dis- 

 placing the air necessary to combustion, just 



