DONATIONS TO THE COLLEGE FUNDS IN 1872. General Extension Fund Law Professorship Fund (Miss Brackenbury) Geology and Mining Professorship Fund Chemical Laboratory Fittings Fund Medical School Fund.. 500 0 0 13,341 0 0 REPORT ON THE PHYSICAL LABORATORY DURING THE SESSION 1871–2. STUDENTS IN ATTENDANCE. There have been altogether eight pupils including Dr. Murray Thomson (of India.) Mr. John Armitage entered for one day a week during the session. Mr. J. R. Ashwell وو Mr. J. H. Poynting Dr. Murray Thomson one day two days two days", two days one day وو ,, every day for one month' OPERATIONS WITH THE BALANCE. This Instrument is by Oertling who is one of the best London makers. Its weights are on the French system, but we have not yet had the opportunity of comparing the kilogramme with some recognised standard. The first operations were made with the view of determining the sensibility of the balance, and how this varied with the weight. In fine the constants for the formula (P-W)a (P+W) + W'% were determined experimentally. The instrument was then used in order to determine the Specific Gravity of well purified Mercury by means of a specific gravity bottle, allowance being made for the buoyancy of the air. Owing to there being only one set of instruments it was found impossible for each student to make a separate determination. The results obtained were very good. Two independent sets of experiments agreed in giving the specific gravity of Mercury = 13.594, which was also the result obtained some years since by Dr. Stewart at the Kew Observatory by the same process. The specific gravity of mercury was also obtained by a different method, namely by weighing it in water, and the result was 13.591 which agrees well with the other determination. Several determinations were likewise made of the Specific gravity of pure Sulphuric Acid. Several determinations were also made of the Expansion of Glass between 0° and 15°C. Unfortunately however during these experiments the specific gravity bottle broke and had to be replaced by another. OPERATIONS WITH THE GONIOMETER. This instrument was first of all properly adjusted, and after that the angles of a large glass prism were measured by its means. The following are two separate determinations of the three angles of this prism: The refractive index of the glass of this prism was also ascertained. This was found to be 1.5287 for the sodium line, a result agreeing well with the determination of the same last year when the index for this line was found to be 1.5286. The refractive indices for other lines were likewise ascertained as follows: (1.52586 For the Lithium line two determinations... 152597 1.53192 For the Thallium line three determinations. 1.53203 1.53192 OPERATIONS WITH WOLLASTON'S GONIOMETER. Some experiments necessarily of less accuracy were also made with Wollaston's Goniometer, in order to ascertain the angles of various crystals. Crystals of Alum and Iceland Spar were used for this purpɔse. OPERATIONS WITH THE SPECTROSCOPE. We are indebted to Dr. Roscoe for the loan of a Spectro Scope with a scale attached to it, and also for some pure salts. Mr. Ashwell has devoted his whole time to Spectrum analysis; and has found the lines for Potassium, Strontium, Lithium, Barium, Rubidium, Calcium, Sodium, Platinum, Gold, Zinc, Tin, Antimony and Cadmium. Several mixtures of salts were made by Mr. Jones in the Chemical Laboratory, and when put into Mr. Ashwell's hands, he detected the nature of the mixtures in all cases by means of the Spectroscope. Mr. Ashwell also ascertained the refractive index and dispersion of a prism for Dr. Roscoe. Mr. Schuster and Mr. Tait have likewise worked at Spectrum analysis. EXPERIMENTS ON HEAT. Instructions has been given in the use of the thermo pile, and several of the students were enabled by its means to see the small radiation of rock salt compared to Glass, and also to see that rock salt is peculiarly opaque for heat radiating from heated rock salt. The comparative radiating power of lamp-black and polished metal was also ascertained; and also the great stopping power of glass for dark heat. HYGROMETRICAL EXPERIMENTS. Dr. Murray Thompson compared the temperature of the dew point as determined by the wet and dry bulb thermometers with that as determined by observation with Regnault's absolute hygrometer. After a considerable amount of practice, it was found that both kinds of observation agreed with one another to within 0°·3F. METEOROLOGICAL OBSERVATIONS. The Barometer has been repaired and the students have been practised in reading this instrument until they agree with one another to about one thousandth of an inch. This instrument and the wet and dry bulb thermometers are read regularly three times a day by Mr. Kingdon and the various students. Similar observations are also made at the residence of Mr. Arthur Schuster. SUNDRY OPTICAL EXPERIMENTS. Experiments were made in order to determine the focal lengths and the indices of refraction of lenses. The following is the result of a set of four such experi ments: Sundry experiments were likewise made with Bunsen's Photometer, in which the light of an ordinary gasburner was compared with that of a standard sperm candle. EXPERIMENTS ON ELECTRIC RESISTANCE. The box of British Association coils was used as a Wheatstone's bridge wherewith to measure the electric resistance of sundry coils, embracing a separate B.A. unit. This when measured against the unit in the box was found to have a value = 1.03. A coil which had at the temperature of 12.3° C. a resistance 11.235, was found to have at 76.25° C. a resistance 11.235, showing an increase in resistance 003 nearly for every degree Cent. EXPERIMENTS ON STRENGTH OF CURRENT AND EFECTRO-MOTIVE FORCE. An arrangement was made for measuring current strength in absolute measure, consisting of a wire coiled round the circumference of a circle having a small magnet in its centre, the current being measured as follows: K2H C= tan d, where C denotes the strength of the curL rent, K the radius of the circle, L the length of the wire, H the horizontal intensity of the earth's magnetism, and d the angle of deviation of the magnet. By this means the electro-motive force of 4 cells of Grove's battery was determined on one occasion, when the battery was in good order, to be (by three separate experiments) 0709, 0713, 0712, while on another occasion when the battery was in bad order this was determined to to be 0678, 0664, 0694 by three similar experiments. EXPERIMENTS ON ELASTICITY. Sundry experiments were also made on the extension of a copper wire suspended from the ceiling and loaded f with various weights: and also on the bending of a beam of wood from which weights were suspended from the middle. The experiments came out consistently with one another. OBSERVATIONS WITH THE DIP CIRCLE. This instrument is by Dover of Charlton, and has been tested at the Kew Observatory. Instruction in the method of observation has been given at the physical laboratory, and an observation was made in the garden of Dr. Stewart on the 28th May. It is expected that a small magnetic house will soon be erected there. ORIGINAL WORK. Mr. Arthur Schuster is making an original investigation regarding the Spectrum of Nitrogen and other Gases and a paper "On the Spectrum of Nitrogen" by him has been communicated to the Royal Society. Some assistance was also rendered at the Physical Laboratory in connection with a paper "On the Influence of Planets on Solar Activity," by Messrs. Warren De La Rue, Stewart, and Loewy, which has recently been published by the Royal Society. Observations on the heating effect produced by rotating a disc in vacuo, and others on temperature are in progress. The Annual Examination of the Students in the Day Classes of the Session 1871-2 having taken place, the results were announced at a public meeting held in the Town Hall, Manchester, on the 21st of June, 1872, and the following Scholarships, Prizes, and Certificates were awarded: WELLINGTON SCHOLARSHIP [Greek Testament], value £20 per annum, tenable for one year. Edwin Jackson. DALTON CHEMICAL SCHOLARSHIP, value £50 per annum, tenable for two years. DALTON JUNIOR MATHEMATICAL £25 per annum, tenable for one year. ENGINEERING CERTIFICATES William Carleton Williams. DALTON NATURAL HISTORY PRIZE, value £15. Arthur Walton Fuller. |