MR JUSTICE CHAPMAN'S LECTURE.

Southland Times, Issue 1601, 5 July 1872, Page 2

MR JUSTICE CHAPMAN'S LECTURE.

His Honor Judge Chapman delivered a most interesting lecture on " The Triumphs of Science," in the Exchange Hall, on Tnesday evening. The Rev. Mr Tanner stated that Judge Chapman had kindly undertaken to deliver a lecture in aid of the Church of England Organ Fund, and requested the meeting to choose a chairman. Mr John Kingaland having been called to the chair, explained that the organ had already been paid for, but before it could be placed in the church, some further expense would have to be incurred, to which the proceeds of this lecture would be applied, and that he was sure all present would feel that they were indebted to His Honor for volunteering his assistance in the good work. In introducing the subject, His Honor said it would hardly be needful to mention that anything like a complete enumeration of the many discoveries and inventions which might be fitly described as triumphs of science would obviously bo impossible within the limits of a lecture. The mere list would be so long as to exhaust the patience alike of speaker and hearers. It would be therefore necessary to select a few of the most remarkable instances in which the mind of man, by the patient and systematic process of scientific enquiry, had been able to penetrate the secrets of nature, and compel her forces to his service. He would commence by describing the circumstances which gave rise to the discovery of those natural laws which led to the invention of the barometer. This instrument, familiarly known as a weather-glass, was in reality a scientific instrument of the utmost delicacy, for measuring the weight and consequently the height of the vertical column o£ atmosphere on any given spot of the earth's surface. It grew out of the common pump. The action of the common suction pump was described in detail, the principle being the raising of water in a tube by producing a vacuum above it by means of a piston. In 1635, certain pumps, constructed in the gardens of one of the Medici family at Florence,. were found to be useless for the purpose for which they were intended, as the water refused to rise in the pipes to a greater height than 32 feet. The mechanical construction of the pumps being excellent, the circumstance gave rise to enquiry. Philosophers were called on to explain it, among the rest Galileo. The reason up to that time assigned for the water rising in the pump, was the generally received axiom, " that nature abhorred a vacuum." Galileo, smarting under the censure of the church, for his heretical discovery of the motion of tb© earth, and unable to solve the difficulty, returned the sulky answer that he supposed that nature abhorred a vacuum only to the extent of 32 feet. After his death, Torricelli, his pupil, remembering experiments of Galileo which proved that air, like other bodies, possessed weight, came to the conclusion that the column of 32 feet of water in the pump was in reality balanced and kept in its position by the weight of the external air on the surface of the water in the reservoir, and that the reason that no more than 32 feet of water could be raised by making a vacuum above it, was that 32 feet of water were equal in weight to a similar column of air,reaching to the limit of the atmosphere. To test this, it was obvious that as mercury was about thirteen times heavier than water, a column of mercury of about 30 inch es should remain suspended in a similar manner in a tube, at the upper end of which a vacuum had been produced. The experiment was tried by Torricelli, and the result confirmed hia theory. Some years later, the theory was submitted to further test by Blaise Pascal, a scientific reasoner of great accuracy, although more generally known by his literary reputation. Pascal conceived the idea that if the column of mercurywere really balanced by the column of external air, the air column would necessarily be shorter and lighter at the top of a mountain than at its base, and the mercury ought to fail accordingly, wheu the instrument was taken to a height. By a series of decisive experiments, conducted on the mountain Puy de Dome, this was further ascertained to be the case, and the question was settled for ever. The barometer is now used as a means of measuring the heights of mountains with the utmost accuracy, by a series of simultaneous observations on the height, and at a point of known altitude near the base, the mercury falling about one inch for every 979 feet gaiued in vertical height. The method of using the barometer to forecast th© weather, by estimating the height of the atmospheric column, the corrections necessary for temperature, and many other details, showing the perfection which the instrument has now attained,, and the successive steps by which that perfection was reached, were also explained with great clearness and precision. The discovery of the asteroids, or aa.

they might more properly be called, the planetoids, was then described as an instance by which the intellect of man, pursuing the methods of science, was enabled to predict the existence of these remarkable bodies before they had been revealed to observation. The distance of the orbits of the planets from the sun appeared to be reeulated by a law, which night be roughly stated thus : — The distance of Mercury from the sun being taken as 2, that of Venus would be 4, of the earth 6, Mars 8. then came a gap, for there was no visible planet in the place represented by 10, but Jupiter was found at 12, and Saturn at 14. This gap Bet astronomers speculating;, but for a long time nothing came of it. The regularity of the planetary orbits was then described, and the slight but perceptible variations, known as "perturbations," from the regular orbit, caused by the proximity of other planets, were clearly explained. The manner in which the existence and place of a planet in this I gap, from observed perturbations in the orbits of Mars and Jupiter, was arrived at by calculation alone, was then described. The correctness of the scientific reasoning was attested by the discovery, on Ist January, 1801, of a small planet, Ceres, in the very place suggested. The bulk of this small planet was not sufficient to account for the effect produced, but three others were discovered shortly after, revolving in close proximity to each other, and almost in a common orbit. Subsequent research, aided by •modern improvements in telescopes, had increased the number to upwards of ninety, all of small size and irregular form, some of them certainly not larger than Stewart's Island. The whole bulk of the planetoids, possibly fragments of ; a larger planet, yet discovered in this gap in the system between Mars and Jupiter, did not amount to more than one-half of the bulk of the Earth, and more probably remained to reward the patient labors of astronomical observers. The triumph of science in this instance was the fact that the existence of these bodies, or a body of similar weight and position, in the planetary system, was proved to be a certain ty by abstract reasoning, before the body itself was seen by the human eye. This discovery, grand as it was, must yield the palm as a triumph, of science and of human genius to the discovery of the planet Neptune, on the very outskirts of the system, in the year 1846. This planet was actually discovered, its existence, position, and mats ascertained, before it had been seen at all. To understand the extent of this achievement, it was necessary to know something of the planet Uranus, the next in the group, which had been discovered by Berschel in 1781. The lecturer here gave a brief but pleasing sketch of the life and labors of that celebrated man, and his less known but almost equally accomplished sister, Miss Herschel, who assisted him for many years in his observations and calculations. The orbit of Uranus having been observed for some time after its discovery exhibited perturbations which could not be referred to the action of any of the known planets of the system. The existence of a planet, exterior to the orbit of Uranus, was then euepected, and it was carefully sought for, by telescopic observation, but in vain. About the year 1842 the idea occurred simultaneously to two mathematicians, Mr Adams of Cambridge, and M. Lever rier of Paris, of undertaking the vast labor of calculating the size and position of this suspected planet, by its effects on the orbit of Uranus. The task was possible, although of herculean magnitude. The lecturer, to illustrate the difficulties to be encountered, compared these calculations to a sum in arithmetic which would take four or five years constant work to bring to a conclusion. About the same time, and unknown to each other, the mathematicians brought their labors to a close. Leverrier wrote to a celebrated observer, Dr Galle of Berlin, to examine a certain spot in the heavens on the night of the 23rd September, where lie would certainly find the suspected planet. A star, not in the catalogue, was observed. Next night it had changed its place, and night after night, as it pursued the course in the heavens laid down for it by the mathematicians, the truth of the discovery was placed beyond a doubt, and this — the grandest of all the triumphs of the human intellect — a scientific prediction absolutely based on reasoning alone, though reasoning of the severest kind — became an accomplished fact. The lecturer then reviewed the history of the electric telegraph, tracing it from the first comparatively rude machine of Professor "Wheatstone to the refined mechanical arrangements used in the telegraphy of the present day. Science, in this instance, had not done so much since the first discovery of the principle, but mechanical ingenuity had done wonder 3. The rapidity of electric communication, so rapid as to be practically instantaneous, was then noticed, and some amusing anecdotes of circumstances arising from the difference of time in places of different longitude connected by telegraph were narrated, notably one of an old gentleman residing some distance to the west of London, who heard of the birth of his grandchild in London on the day preceding the actual occurrence, and yet the information was correct, the event having taken place near midnight, and the difference of time between the two places explaining the apparent impossibility. Mr Lowe, Chancellor of the Exchequer, in the year 1870,. finished bis budget speech in the House of Commons at midnight. That hour represented 5 a.m. next day at Calcutta. In spite of this loss of five hours, so perfect were the telegraphic arrangements, that the speech was printed in the Calcutta morning papers, and was on the breakfast tables of the inhabitants by nine o'clock, or four hours alter its delivery. The last subject treated by the lecturer was the discovery and progress of the art of photography. After dwelling on the happy social effects

which he believed might be assigned to the prevalent and increasing practice of collecting and exchanging cartes de visite, the lecturer gave ilustrations of the manoer in which photography was applied to the service of science, especially astronomical science, as in the case of aolar eclipses, and other astronomical phenomena, of which trustworthy records, far exceeding in value those which could be procured by any other means, were thus obtained, and from the inspection and comparison of these photographs great and important discoveries had been made. The lecturer concluded by pointing out that in all the cases he had adduced, the human mind, by following with determinatioa and perseverance the path of scientific enquiry, had arrived at discoveries of the grandest kind, and reduced to matters of certain and definite knowledge the results of conjectures, which, in the first instance, might seem too extravagant even for the wildest flights of imagination. The foregoing ia of course only a very condensed resume' of the lecture, which occupied an hour and a half in delivery, and was listened to with the utmost interest. The audience, we regret to say, was smaller than it ought to have been on such an occasion. A vote of thanks to the lecturer closed the proceedings.