WELLINGTON ATHENÆUM.

New Zealand Spectator and Cook's Strait Guardian, Volume VIII, Issue 730, 31 July 1852, Page 2

WELLINGTON ATHENÆUM.

On Thursday evening l)r. Kalph delivered his third and concluding lecture in the hall of the Institution ; there was a very good attendance of members, who appeared to be highly pleased at the manner in which the lecturer treated his subject, which he illustrated by several diagrams. After referring to the subject of the former lecture, namely the properties of oxygen, hydrogen, nitrogen, and carbon, the lecturer went on to show that these four elements, or simple substances, entered into the composition of all organised' bodies. In the vegetable kingdom plants were found to be made up of organs called cells and vessels, or communicating passages, by means of which they obtained, eitherfrom the earth or the atmosphere, those materials with which they could build up their particular structures. He then went on to show that ithe air contained the four elements which were so necessary to the life of plants and animals, namely, the atmosphere was a mixture of nitrogen and oxygen, and had besides diffused through it carbonic acid gas, which yielded carbon ; and there was also the vapour of water, into which hydrogen entered very largely. Thus, the four principal elements were always at hand for the supply of the wants of the organic kingdoms. Then the lecturer explained the way in which fluids in the earth, and vapour of water charged with gases, could find entrance into the tissues of plants, by exhibiting the experiment of Dutrochet, in which it was found that a sac composed of membrane or bladder, and filled with syrup and plunged into water, was immediately filled with water through the invisible apertures in its structure; and that the cells in roots of plants were 'similarly circumstanced, as they contained gummy or sugary juices in most of their cells, and absorbed water charged with various soluble substances, as carbonic acid gas, saline matters, &c. Next, the principal vegetable products were noticed, as starch, gum, and sugar, and it was. found that these were closely related to each other in their chemical composition. Starch was a compound of twelve parts of carbon, ten of hydrogen, and ten of oxygen. Gum exactly the same. Sugar, twelve parts of carbon, nine of hydrogen, and nine of oxygen, so that starch could easily be converted in the cells of a plant into gum or svgar — a result which the chemist obtained by subjecting starch to the action of weak acid, when it became -converted into a gummy substance ; and, by continuing the action, a kind of grape sugar was obtained. But the chemist, although having all the necessary elements at hand, could not combine them into stareh — a combination only capable of being effected in the cells of plants. The change from starch into gum or sugar in plants was brought about by t)ther substances called diastase and dextrine, which were stored up in small quantities with the starch, and served the purpose of commencing the change of the starch into gum or sugar, which soluble substances were then carried into all the tissues of plants, and from the latter (sugar) starch was again deposited either in the seeds or in the formed structures, which were to do their share of work in the economy of the plant during the next season. The lecturer then alluded to the quantity of carbonic acid gas which was said to exist in the atmosphere, in the proportion of one in a thousand parts; and, by calculating the pressure of the air upon a square foot, it might be seen that a pressure of 2016 would give 2lbs. of carbonic acid gas" in a column of air of those dimensions, and that the 2lbs. of gas contained rather more than half a pound ot carbon. Some calculations had "been made by philosophers, and the quantity of carbon supposed to exist in the whole atmosphere was estimated at 3000 billions of pounds, a quantity more than that now existing in the form of plants. The lecturer then concluded by stating, that it was now generally admitted that carbon, hydrogen, nitrogen, and oxygen, were the constituents of everything that either had lived, or was still living ; and that the greater part of organized matter has been formed of these four elements ; and that, although man made use of but one hundredth part of the plants which nature yielded, yet, without vegetation, both food, and the life sustaining material oxigen, would be cut off were plants to cease to exist, as they were the agents by which the carbonic acid gas, thrown into the air from the lungs of animals, was decomposed into carbon, which was retained by the plant; and oxygen, which was liberated for the use of the animal. And the importance of the gaeeous veil of the earth was seen in the fact, that it was an agent of nature which assisted in the preparing of the mineral or inorganic materials for the use of plants, and was the source of food to plants, and the supporter of respiration to animals ; and that it was apparent that -at one time substances constituted parts either of the atmosphere or of the black soil of the earth, and, at another, formed the component parts of living plants or animals. The lecture lasted nearly two hours, during which the learned gentleman was repeatedly applauded.