IS45.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



183 



pressure, as otherwise ebullition would inevitably take place : but I am not 

 aware that the teniiierature has ever been examined with a thermometer 

 under these circumstances, and it would be by no means easily done. 



I shall probably scarctly be believed when I say that even liquid iiilphu- 

 rous acid does not, when contained in a red-hot vessel, and in the suheroidal 

 state, boil in vacuo. 



It ia also stited that if a piece of ice bo thrown into a red-hot cru- 

 cible part of the ice becomes water in the spheroidal state, and the 

 rest remains unmelted within the globule. Another very important 

 f.ict, which seems to have been ascertained, was that spheroidal liquuls 

 did not actually toucli the liquid metal. 



If silver be touched with nitric acid it is rapidly corroded, and in a short 

 time dissolved. Hut if a quantity of nitric acid be poured into a crucible or 

 dish of silver, sufficiently hot to induce the spheroidal state, no corrosion 

 whatever will take place ; clearly proving that the acid is at no linie in abso- 

 lute contact with the metal. That this is not owing to any deficiency in the 

 strength of the acid may be seen by placing in the spheroid a piece of cold 

 silver, when violent action of course takes place, nitrous fumes being given 

 off, and nitrate of silver formed. 



A remarkable effect may be produced, owing to this repulsion between 

 liquids and heated solids, if a large spheroid of water be formed on a surface 

 nearly Hat, and a small bar of while or red-hot iron be then thrust into the 

 middle of it. Contact l)eing impossible between the bar and the water, the 

 latter forms a ring at some little distance from the heated bar, presenting 

 very much the appearance of Saturn and his ring. Whether any real analogy 

 exists between the two effects, or whether the causes be in any way con- 

 necteil, further researches into the nature of tliat anomalous appendage of 

 the planet may perhaps decide. 



Mr. Bowman concludes his valuable history of his experiments by 

 shewing their application to the oxpUmation of explosions of boilers. 



If lieat be applied to water contained in an open boiler, the temperature of 

 the water will of course continue to rise until it reaches 212°, when the 

 elastic force of the steam is sufficiently great to overcome the pressure of the 

 atmosphere, and the water boils. If the heat be still continued, the whole 

 of the water will, as is well known, boil away, leaving the vessel empty: but 

 as long as any liquid remains, the temperature of the vessel never rises above 

 212", owing to the absorption of heat by the steam. 



As soon as the boiler is empty, however, its temperature of course rapidly 

 rises, and may reach a red, or even white heal, provided the furnace be suffi- 

 ciently powerful. 



If water be now gradually thrown into the overheated boiler, we know 

 from what has already been said, that it will pass at once into the spheroidal 

 state, and will continue at 205°, until, from some cause or other, it is per- 

 mitted to come in contact with the heated surface, when violent ebullition 

 immediately takes place, an enormous quantity of steam is instantaneously 

 produced, and, if the vessel be a closed one, as is the case with steam boilers, 

 an cvplosinn is the almost inevitable result. 



An experiment exceedingly easy of performance is sufficient to illustrate 

 this. Let a large spheroid be formed in a vessel of platinum, or copper ; so 

 long as the heat is applied to the latter, the water never shows the least sign 

 of boiUng ; but if the lamp be extinguished, and the vessel allowed to cool 

 a little, the water suddenly comes in contact with the metal, and an enor- 

 mous quantity of steam is instanlly formed. 



He then shows that it is a positive fact that steam boilers may be- 

 come red-hot even while containing water, owing to the water assum- 

 ing the spheroidal state, and tliat if by cooling the v^'ater come in con- 

 tact with the metal steam is generated with such rapidity that the boiler 

 instantly bursts. Our last extract shall be from the practical rules 

 which the experiments suggest for the prevention of explosions, and 

 in concluding our notice of the pamphlet we unhesitatingly recommend 

 it as well worthy of a most attentive perusal. 



15c careful that the boiler is kept as free a possible from earthy incrusta- 

 tions, which, if allowed to accumulate, form, in fact, a boiler of stone inside 

 the iron one, and thus retard the passage of heat from the fire to the water, 

 until the iron has become more or less overheated. 



Never let there be a deficiency of water in the boiler, since when that 

 happens, the latter may become heated almost indefinitely, and is conse- 

 quently sure to render water spheroidal when thrown in ; when an explosion 

 will be (without great care) almost certain. 



And lastly. If it be known that, owing to any cause, the water in a boiler 

 has already become spheroidal, instantly stop tiie supply of water, and lake 

 care that llie fire is well kept up until the wlioleof the water has evaporated ; 

 when that is the case, the boiler should be allowed to cool to its natural 

 temperature, when water may be added and the fire rekindled. 



^ Nomenclature of Colours. By D. R. H.iv. Edinburgh .ind London : 

 Blackwood and .Sons. Svo. pp. 72. 



The author of this work is kiiov\n to the public by several preceding 

 books of an analogous description. Tin.' subjijcl is one which pos- 



sesses a great interest on account of its importance witli reference to 

 the manufacturer. It is obvious that a systematic classification of 

 colours, from its superior accuracy and convenience, would be a great 

 improvement on the loose indefinite terms now in use. The abject of 

 imblishing the present volume is stated by the author in the following 

 terms :— 



My purpose is to attempt to classify, arrange, and define colours, in order 

 10 enable those who are following such branches of study, as well as the 

 artist, more easily to comprehei.d the nature of each particular hue, tint, and 

 shade, and the relation that it bears to the primary elements of light, dark- 

 ness, and colour. 15y this knowledge a description may be given where no 

 proper name can be ai)plied, and every compound become as .veil understood 

 as the primary elements, yellow, red, and blue. 



The work is illustrated by specimens of a great many coif .:s and 

 tints, some of them very brilliant. The classification adopt ' is a 

 very good one ; the " primary" colours are red, blue, and yell...., Ihc 

 " secondary" are those arising from the combination of every two of 

 the preceding, the "tertiary" are those arising from combinations of 

 the secondary. This arrangement is very convenient for practical 

 purposes, but l\Ir. Hay's speculations on the physical theory of ligiit 

 are of a very sorry character indeed. The following will suffice for a 

 specimen. — 



According to the language generally employed by writers upon colour, 

 ; ellow, red, and blue are said each to absorb a certain portion of the rays of 

 Ught, and reflect or transmit the remainder. But I cannot consider this doc- 

 trine to be correct, while I believe colour to be produced by the joint in- 

 fluence of light and shade, as already mentioned. We know that fire is pro- 

 duced by combustion, and that the active agent is oxygen, and the passive 

 agent the body consumed, by which joint operatiou fire is produced. In like 

 mauner, light is the active and darkness the passive agent in the production 

 of colour ; and each of the primaries is thus the effect of the principles of 

 light and darkness acting together upon the visual organ, and producing by 

 their joint operation a colour. 



V7e are sorry Mr. Hay " cannot consider" the doctrine respecting 

 the absorption of rays " to be correct," because we almoit fear that 

 philosophers generally will be inclined to defer more to the names of 

 Huygens, Fresnel, Sir William Hamilton, &c., than to that of Hay ; 

 and 7Hai/ perhaps prefer the splendid analytical investigations of the 

 former to the unsupported dicla of the hitler. Of the meaning of the 

 phrase " light is the active and darkness the passirc agent" v\'e have 

 not even a glimmering conception, nor do we see what analogy " com- 

 bustion" lias to colour. This philosophy, on the whole, appears of 

 that mysterious kind which based the science of pneumatics on Dame 

 Nature's " abhorrence of a vacuum" — the fastidious jade ! 



Mr. Hay has some crotchet about colour being a mixture of light 

 and darkness, (as if darkness were a positive existing principle and 

 anything moie than the absence of light). Well, — when he opens his 

 shutters of a morning, does he find that, as more and more light is 

 admitted to the room, the colour of objects within it changes ? He 

 also oftijrs another theory at the end of the book, which, as we do not 

 more than half understand it on account of its excessive profundity, 

 shall be given in the original words. 



The fact has also been ascertained that the atmosphere, when pure, is 

 composed of two gases, with the admixture of a small proportion of aqueous 

 vapour and carbonic acid. * * * Now, as the atmosphere is admitteil 

 lO be a body, may we not suppose that it is constituted like other elastic 

 bodies, though it cannot, like those that are solid, be brought withiu the 

 sphere of microscopical investigation, and that this aqueous vapour is dis- 

 tributed throughout the atomic interstices in the form of an infinitely minute 

 and symmetrically reticulated fibrous tissue, susceptible of tension and at- 

 tenuation, like that known to exist in animal and vegetable substances ? 



By such a supposed distribution of the aqueous vapour, an independent 

 vehicle of sound is at once supplied, and the gaseous elcmeuts of the atmos- 

 phere left to perform their wonderful and important duties in the economy 

 <jf the creation undisturbed. * * * The supposition which I have 

 hazarded, will also satisfactorily account for the greater facility with which 

 sound is transmitted in the lower regions of the atmosphere, where the rela- 

 tive proportion of the aqueous vapour to that of the gaseous elements is 

 greater than in its higher regions. 



From all whicli we may safely conclude that sounds depend on the 

 hygrometer and barometer; that in dry weather the human voice 

 sinks to a whisper, and on a vi-ry rainy <lay oral communication may 

 bo maintained between London and York. 



The work abounds in numerical tables of the " powers" of colours, 

 but as these tables seemed in some way connecteil with Mr. Hay's own 

 theory of light, wc have not thought it worth while to examine llieni. 



