HA RD WICKE'S SCIENCE- G OSS I P. 



1S1 



II. Tomlinson has endeavoured to throw some light 

 upon the mystery by testing the variations of internal 

 friction of the metal at different temperatures, the 

 method adopted being that of suspending a wire 

 vertically, heating it by an electric current, and 

 noting the period of horizontal vibration when the 

 wire is twisted. At 550° (Centigrade) the internal 

 friction rises rapidly, and still more rapidly at 1000 , 

 at which temperature the wire comes to rest after two 

 or three vibrations. From Iioo to 1200 it seems 

 to decrease. At 550 the magnetic and thermo- 

 electric properties also change. At 1000 heat also 

 becomes latent. When iron has been strained by 

 bending or hammering, the strained portion appears 

 clouded as the cooling proceeds. This is attributed 

 to the more rapid cooling of the strained part, which, 

 according to Mr. Tomlinson, has a lower specific heat 

 than the unstrained portions. In well-annealed iron 

 recalescence cannot be detected. 



Rapid Evaporation. —If I remember rightly it 

 was Sydney Smith who defined woman as a biped 

 who refuses to reason and who lights a fire on the 

 top. Woman was avenged when it was proved that 

 the best method of preventing smoke and economising 

 fuel in an ordinary open grate is to light the fire at 

 the top and allow it to gradually burn downwards. 

 By doing so the hydro-carbon vapours generated in 

 the first stage of combustion of the coal, have to pass 

 through the fire above, and are there completely 

 burned with full supply of oxygen, and therefore no 

 smoke is generated. This proceeding corresponds to 

 that of firing a boiler furnace by pushing the fully 

 incandescent fuel farther back on the long bars and 

 supplying fresh fuel in front. 



A German chemist, W. Hempel, has carried the 

 feminine paradox still further. He finds that the 

 most rapid and generally effective method of evapo- 

 rating liquids, is to apply the heat above their 

 surface instead of at the bottom of the vessel containing 

 them. For this purpose he uses a Siemens' inverted 

 regenerative gas-burner, (other inverted burners, of 

 which so many are now in use, will answer the 

 purpose,) bringing the flame as near as possible to the 

 surface. There is no ebullition and consequently no 

 spirting, an important advantage in many chemical 

 operations, especially where evaporation is involved in 

 an analytical process. He finds that no appreciable 

 amount of sulphurous acid from the gas is absorbed 

 by the liquid. 



The Specific Gravity of Liquids. — A. B 

 Taylor ("Chemical News, vol. li. p. 138) proposes 

 a very simple method of ascertaining this. It is to 

 take a solid of known specific gravity, and of this 

 weigh as many grains as correspond to its specific 

 gravity, and then weigh it in the liquid to be tested. 

 The loss of weight in grains expresses the specific 

 gravity of the liquid. 



The principle of this will be understood by 



remembering, that specific gravity tables express the 

 weight of a given bulk of solids and liquids as 

 compared with an equal bulk of distilled water. 

 Therefore if Mr. Taylor's method be applied to 

 distilled water, the result will be unity, whatever solid 

 be used. If, for example, the specific gravity of the 

 solid be i*o, it means that bulk for bulk it weighs the 

 same as water, therefore, if one grain of this is 

 weighed in water it will displace exactly its own bulk 

 of water and neither float nor sink, will weigh 

 nothing in the water, i.e. will lose one grain. The 

 specific gravity of platinum is 2\\. Therefore 2i£ 

 grains will have exactly the same bulk as the solid 

 above supposed, or that bulk of water, and the loss 

 again will be 1. But if the liquid were, say \\ times 

 as heavy, bulk for bulk, as distilled water, this bulk 

 of platina will have to displace or push upwards \\ 

 times as much weight of fluid in order to put itself 

 below its surface, and thus will lose \\ grains of 

 weight in such liquid as against the one grain lost in 

 water. 



NOTES ON rHTHIRIUS INGUINALIS. 



TWO or three specimens of this insect were sent 

 to me to be mounted. On examination one of 

 them proved to have feet of what I take to be a 



Fig. 75. — [a) External and internal terminal claws. 

 P. ingiiinalis. 



Fig. 76.— (o) Ovum? P. inguinalis. 



somewhat peculiar structure. Within the terminal 

 joint of each foot there is a terminal claw, which is 

 rather longer than the external terminal claw. This 



