i8;i.] 



Heat. 



555 



nearly so, upon the plate beneath, the temperature of which is, under the 

 abnormal conditions, considerably above the boiling-point of the water — and 

 all the conditions necessary for the production of the spheroidal state are 

 present. If the rarefaction is carried until the barometer indicates 10 cm. 

 (about 4 inches) of mercury, and the water-bath is heated to about go° C, the 

 experiment will succeed without the slightest difficulty, and the spheroids 

 obtained will evince an energetic movement. The experiment is not a mere 

 physical curiosity, but possesses an importance which our educated readers 

 will doubtless have already appreciated, inasmuch as it is decisive in con- 

 firming the theory of the spheroidal state. It proves that the force which 

 sustains the globule obeys the laws which govern the tension of vapours. 



Dr. Andrews has examined the action of heat on bromine. If a fine tube is 

 filled one-half with liquid bromine and one-half with the vapour of bromine, 

 and after being hermetically sealed is gradually heated till the temperature is 

 above the critical point, the whole of the bromine becomes quite opaque, and 

 the tube has the aspect of being filled with a dark red and opaque resin. A 

 measure of the change of power of transmitting light in this case may be 

 obtained by varying the proportion of liquid and vapour in the tube. Even 

 liquid bromine transmits much less light when heated strongly in an hermeti- 

 cally-sealed tube than its ordinary state. 



A number of devices, some of them simple, others complex, have from time 

 to time been described for showing the reciprocal combustion of the elements 

 of water, and experiments of a similar nature. Most, if not all of these, how- 

 ever, as will be found upon testing, either do not entirely remove the danger of 

 an explosion from the operator, or they require the exercise of an unusual 

 amount of care and dexterity to be used with success. 



The accompanying arrangement, which is of the most simple character, and 

 which we saw for the first time on the lecture table of Professor Himes, 

 we have since repeatedly used to show the burning of oxygen, air, chlorine, &c, 

 in hydrogen, burning gas, or hydrocarbon vapours. -p- a 



The experiment can be performed with such 

 ease that it is worthy of notice. 



The arrangement consists of a cylinder of 

 glass, about a foot or a foot and a half in length 

 (the kind used commonly as chimneys for the 

 argand-burner can be had of proper length). 

 Tnis is furnished above and below with a cork ; 

 the one at the upper end has one, that below has 

 two, glass tubes of the form shown in figure. 

 The whole affair is supported from the retort 

 stand. The hydrogen (in the H and O experi- 

 ment) is admitted through the upper tube ; when 

 it has completely displaced the air it is ignited 

 below — the cork having been removed — and the 

 supply is regulated until only a weak hydrogen 

 flame remains. The oxygen supplied through 

 the straight tube in the lower cork is now turned 

 on slightly, and the cork fitted into its place. 

 The flame of hydrogen at the opening is extin- 

 guished, but the oxygen, in passing up through 

 it, is ignited, and burns now in the centre of the 

 cylinder. The surplus of the hydrogen escapes 

 now from the second tube below, and can be 

 there ignited. This last flame serves the purpose of a good indicator, by which 

 the supply of gases in the cylinder can be regulated, and which, of course, 

 leaves the size of the flame at the will of the operator. Once in operation, the 

 experiment may be left to take care of itself for the remainder of the hour. 



After briefly referring to the experiments of the Florentine Academicians, 

 and of Huyghens (1667), on tne force exerted by the freezing of water in 

 closed metallic vessels, M. Boussingault relates a series of experiments made 



VOL. VIII. (o.s.) — VOL. 1. (n.s.) 4 c 



