When the dense fluid occupies the necks which join two cavities, it performs the singular function of a fluid valve, opening and shutting itself according to the expansions or contractions of the other fluid. The fluid valves thus exhibited in action may suggest some useful hints to the mechanic and the philosopher, while they afford ground of curious speculation in reference to the functions of animal and vegetable bodies. In the larger organizations of ordinary animals, where gravity must in general overpower, or at least modify, the influence of capillary attraction, such a mechanism is neither necessary nor appropriate; but, in the lesser functions of the same animals, and in almost all the microscopic structures of the lower world, where the force of gravity is entirely subjected to the more powerful energy of capillary forces, it is extremely probable that the mechanism of immiscible fluids and fluid valves is generally adopted.
In several cavities in minerals I have found crystallized and other bodies, sometimes transparent crystals, sometimes black spicular crystals, and sometimes black spheres, all of which are moveable within the cavity. In some cavities the two new fluids occur in an indurated state, and others I have found to be lined with a powdery matter. This last class of cavities occurred in topaz, and they were distinguished from all others by the extraordinary beauty and symmetry of their form. One of these cavities represented a finely ornamented sceptre, and, what is still more singular, the different parts of which it is composed lay in different planes.
When the gem which contains the highly expansive fluid is strong, and the cavity not near the surface, heat may be applied to it without danger; but in the course of my experiments on this subject, the mineral has often burst with a tremendous explosion, and in one case wounded me on the brow. An accident of the same kind occurred to a gentleman who put a crystal into his mouth for the purpose of expanding the fluid. The specimen burst with great force and cut his mouth, and the fluid which was discharged from the cavity had a very disagreeable taste.
In the gems which are peculiarly appropriated for female ornaments, cavities containing the expansive fluid frequently occur, and if these cavities should happen to be very near the surface or the edge of the stone, the fever heat of the body might be sufficient to burst them with an alarming and even dangerous explosion. I have never heard of any such accident having occurred; but if it has, or if it ever shall occur, and if its naturally marvellous character shall be heightened by any calamitous results, the phenomena described in the preceding pages will strip it of its wonder.
There are no facts in chemistry more interesting than those which relate to the changes of colour, which are produced by the mixture of fluids, and to the creation of brilliant colours by the combination of bodies in which no colouring matter is visible. Facts of this kind are too common and too generally known to require to be noticed in a work like this. The art of producing such changes was known to some of the early impostors, who endeavoured to obtain a miraculous sanction to their particular dogmas. Marcos, the head of one of the sects that wished to engraft paganism upon Christianity, is said to have filled three transparent glasses with white wine, and while he prayed, the wine in one of the glasses became red like blood, that in another became purple, and that in the third sky-blue. Such transformations present no difficulty to the chemist. There are several fluids, such as some of the coloured juices of plants, which change their colour rapidly and without any additional ingredient: and in other cases, there would be no difficulty in making additions to fluids which should produce a change of colour at any required instant.
A very remarkable experiment of an analogous nature has been publicly exhibited in modern times. Professor Beyruss, who lived at the court of the Duke of Brunswick, one day pronounced to his highness that the dress which he wore should during dinner became red; and the change actually took place, to the astonishment of the prince and the rest of his guests. M. Vogel, who has recorded this curious fact, has not divulged the secret of the German chemist; but he observes, that if we pour lime-water into the juice of beet-root, we shall obtain a colourless liquid; and that a piece of white cloth dipped in this liquid and dried rapidly, will in a few hours become red by the mere contact of air. M. Vogel is also of opinion that this singular effect would be accelerated in an apartment where champagne or other fluids charged with carbonic acid are poured out in abundance.
Among the wonders of chemistry we must number the remarkable effects produced upon the human frame by the inhalation of paradise or intoxicating gas, as it has been called. This gas is known to chemists by the name of the nitrous oxide, or the gaseous oxide of azote, or the protoxide of nitrogen. It differs from atmospheric air only in the proportion of its ingredients, atmospheric air being composed of twenty-seven parts of oxygen, and seventy-three of nitrogen, while the nitrous oxide consists of thirty-seven parts of oxygen, and sixty-seven of nitrogen. The most convenient way of procuring the gas is to expose nitrate of ammonia in a tubulated glass retort to the heat of an Argand’s lamp between 400° and 500° of Fahrenheit. The salt first melts; bubbles of gas begin to rise from the mass, and in a short time a brisk effervescence takes place, which continues till all the salt has disappeared. The products of this operation are the nitrous oxide and water, the watery vapour being condensed in the neck of the retort, while the gas is received over water. The gas thus obtained is generally white, and hence, when it is to be used for the purposes of respiration, it should remain at least an hour over water, which will absorb the small quantity of acid and of nitrate of ammonia which adhere to it. A pound of the nitrate of ammonia will in this way yield five cubic feet of gas fit for the purpose of inhalation.
It was discovered by Sir Humphrey Davy, that this gas could be safely taken into the lungs, and that it was capable of supporting respiration for a few minutes. In making this experiment he was surprised to find that it produced a singular species of intoxication, which he thus describes: “I breathed,” says he, “three quarts of oxide from and into a silk bag for more than half a minute without previously closing my nose or exhausting my lungs. The first inspiration caused a slight degree of giddiness. This was succeeded by an uncommon sense of fulness in the head, accompanied with loss of distinct sensation and voluntary power, a feeling analogous to that produced in the first stage of intoxication, but unattended by pleasurable sensations.” In describing the effects of another experiment, he says, “Having previously closed my nostrils and exhausted my lungs, I breathed four quarts of nitrous oxide from and into a silk bag. The first feelings were similar to those produced in the last experiment, but in less than half a minute, the respiration being continued, they diminished gradually, and were succeeded by a highly pleasurable thrilling, particularly in the chest and the extremities. The objects around me became dazzling, and my hearing more acute. Towards the last respiration the thrilling increased, the sense of muscular power became greater, and at last an irresistible propensity to action was indulged in. I recollect but indistinctly what followed; I knew that my motions were varied and violent. These effects very rarely ceased after respiration. In ten minutes I had recovered my natural state of mind. The thrilling in the extremities continued longer than the other sensations. This experiment was made in the morning; no languor or exhaustion was consequent, my feelings through the day were as usual, and I passed the night in undisturbed repose.”
In giving an account of another experiment with this gas, Sir Humphrey thus describes his feelings: “Immediately after my return from a long journey, being fatigued, I respired nine quarts of nitrous oxide, having been precisely thirty-three days without breathing any. The feelings were different from those I had experienced on former experiments. After the first six or seven respirations, I gradually began to lose the perception of external things, and a vivid and intense recollection of some former experiments passed through my mind, so that I called out, ‘What an annoying concatenation of ideas!’”
Another experiment made by the same distinguished chemist was attended by still more remarkable results. He was shut up in an airtight breathing-box, having a capacity of about nine and a half cubic feet, and he allowed himself to be habituated to the excitement of the gas, which was gradually introduced. After having undergone this operation for an hour and a quarter, during which eighty quarts of gas were thrown in, he came out of the box and began to respire twenty quarts of unmingled nitrous oxide. “A thrilling,” says he, “extending from the chest to the extremities, was almost immediately produced. I felt a sense of tangible extension highly pleasurable in every kind; my visible impressions were dazzling and apparently magnified; I heard distinctly every sound in the room, and I was perfectly aware of my situation. By degrees, as the pleasurable sensation increased, I lost all connexion with external things; trains of vivid visible images rapidly passed through my mind, and were connected with words in such a manner as to produce perceptions perfectly novel. I existed in a world of newly connected and newly modified ideas. When I was awakened from this same delirious trance by Dr. Kinglake, who took the bag from my mouth, indignation and pride were the first feelings produced by the sight of the persons about me. My emotions were enthusiastic and sublime, and for a moment I walked round the room, perfectly regardless of what was said to me. As I recovered my former state of mind, I felt an inclination to communicate the discoveries I had made during the experiment. I endeavoured to recall the ideas; they were feeble and indistinct. One recollection of terms, however, presented itself, and with the most intense belief and prophetic manner I exclaimed to Dr. Kinglake, ‘Nothing exists but thoughts; the universe is composed of impressions, ideas, pleasures, and pains!’”