SCIENCE. 



3i5 



vibration occurred in the case of a large metallic mass. 

 An intermittent beam of sunlight was focussed upon a 

 brass weight (1 kilogram), and the surface of the weight 

 was then explored with the microphone shown in Fig. 2. 

 A feeble but distinct sound was heard upon touching the 

 surface within the illuminated area and for a short dis- 

 tance outside, but not in other parts. 



In this experiment, as in the case of the thin dia- 

 phragm, absolute contact between the point of the micro- 

 phone and the surface explored was necessary in order 

 to obtain audible effects, xnow, I do not mean to deny 

 that sound waves may be originated in the manner sug- 

 gested by Mr. Preece, but I think that our experiments 

 have demonstrated that the kind of action described by 

 Lord Raleigh actually occurs, and that it is sufficient to 

 account for the audible effects observed. 



ASTRONOMY. 



On the 23rd ultimo, Mr. E. L. Larkin, a subscriber 

 and contributor to this journal, telegraphed to Professor 

 Swift, of Rochester, the discovery of a comet in the con- 

 stellation of Auriga ; but as others have since made the 

 same claim, the priority of discovery awaits confirmation 

 by those who dispense the pecuniary reward offered by 

 Mi. Warner for all comets discovered during the present 

 year. 



We reserve until next week our report on this interest- 

 ing celestial object, by which time our correspondents 

 will have worked out the results of their observations, 

 which have been delayed by atmospheric and other diffi- 

 culties. The comet is now plainly visible, and American 

 astronomers are on the alert to thoroughly examine it with 

 all the appliances which modern science has placed at 

 their command. At the date of our writing nothing re- 

 liable has been determined by actual observations, but 

 some interesting facts, based on preliminary and partial 

 observations, have been communicated, which, if accepted 

 with reserve, pending final results, may be found useful 

 to those directing their attention to the comet. 



Professor Henry Draper is said to have made several 

 successful photographs of the erratic stranger. Profes- 

 sor C. A. Young, of Princeton, has examined its spectrum, 

 and reports that that of the nucleus was continuous, 

 while that of the coma was sensibly coincident with the 

 spectrum of the Bunsen burner flame. As seen directly 

 in the 9% inch equatorial, with eye-pieces of the lowest 

 power, cn the evening of the 26th, the nucleus was small 

 and bright, with five bright jets of unequal length project- 

 ing from it a short distance. The tail showed three 

 maxima of brightness, of which the brightest was near 

 the axis, and was quite convex in the direction of increas- 

 ing right ascension. On the 26th he states the spectrum 

 was about the same, but the nucleus, instead of showing 

 jets as before, was nearly surrounded by an envelope. 



Professor Boss of the Dudley Observatory determines 

 the diameter of the nucleus to be seven seconds or 1 500 

 miles, at an estimated distance of 45,000,000 of miles. 



Professor Asaph Hall considers it most probable that 

 the comet is identical wiih that discovered by Professor 

 B. A. Gould at Buenos Ayres of the 1st of June. On the 

 26th ultimo an observation was made at the naval ob- 

 servatory, Washington, which indicated "the position of 

 the comet at its lowest culmination, obtained with the 

 transit circle, was at 11 h. 27. P. M., Right ascension 

 5 h., 48 m., 384-100 s., North declination, 57 deg., 40 m., 

 52 sec. 



The Lunar Eclipse.— The eclipse of the moon on 

 June 11 was seen under favorable conditions at the Naval 

 Observatory, Washington. The only observations of 

 importance were observations of occultation of B. A. C. 

 5862, and two faint stars during the eclipse. 



THE OHM. 



A British Association committee has been reappointed 

 for the remeasurement of the Ohm, and of other units. It 

 is not to their work, however, that we wish now to draw 

 attention, but rather to a good stroke in the right direction, 

 done in the Cavendish laboratory by Lord Rayleigh with the 

 assistance of Dr. Schuster and others. The old British 

 Association apparatus has been fitted up again, with such 

 improvements as the criticism of nearly twenty years has 

 suggested. It will be remembered that this is the only 

 method in which the measurement of transient currents by 

 ballistic galvanometers is not employed. A circular coil 

 of insulated wire forming a closed circuit rotates about a 

 vertical axis, and the electrical current induced in it by the 

 eatth's magnetism gives a steady deflection to a magnetic 

 needle at its centre. The manifold precautions, calcula- 

 tions and corrections which have to be entered into by the 

 experimenters are given by Professor Fleeming Jenkin and 

 others. One important correction is that which is due to 

 the self-induction of the coil which retards the current, 

 and a most important fact has been brought to light by 

 Lord Rayleigh, namely, that this self-induction is consider- 

 ably greater than it was thought to be by the original com 

 mittee. Professor Rowland, assuming that an unknown 

 error existed proportional to the square of the speed of the 

 rotation, has found that the original experiments of the 

 committee lead to the result that the Ohm is 0.74 per cent, 

 smaller than it was intended to be, and his own experi- 

 ments lead to its being 0.89 smaller. Kohlrausch found it 

 nearly 2 per cent, too great, and Weber thought it correct. 

 The Cavendish laboratory experiments lead to its being 

 1.05 per cent, too small, and the elaborate paper to the 

 Royal Society in which this result is given promises a re- 

 determination with new apparatus on the same principle. 

 In making the present determination a new method of sus- 

 pension of the needle, a stroboscopic method of measure- 

 ment of the speed — the old governor and the tinkling bell 

 being discarded — and driving the coil by means of a water 

 turbine instead of by hand, are some of the improvemet ts 

 which have been introduced. 



It is to be remembered that no re-measurement of the 

 Ohm can ever effect our use of it as a standard. It is no 

 longer to be regarded as exactly equal to one thousand 

 million C. G. S. units, but this is of no more consequence 

 than the fact that one gramme is no longer regarded as 

 being exactly equal to the mass of a cubic centimetre ot 

 water at 4° C. — The Electrician. 



ALCOHOL IN WATER AND AIR. 



Aninteresting discovery has been brought before the Acad- 

 emy of Sciences by M. Muntz, Chief of the laboratories be- 

 longing to the Agricultural Institute. He has found that al- 

 cohol is distributed throughout the universe, in the sun, air, 

 water of the ocean and streams. It is a known fact that 

 fermentation is a general phenomena in air, water and earth ; 

 This fermentation gives off CO 2 , and as a necessary conse- 

 quence, alcohol. This is what the experiments of M. 

 Muntz have demonstrated ; he has been able to prove the 

 presence of alcohol in water, etc., by reducing the alcohol 

 to an iodofortn state by means of iodate and carbonate of 

 soda. The precipitate which is obtained even in the pres- 

 ence of a millionth quantity of alcohol, affects the crystal- 

 line form of the snow examined under the microscope. 

 The alcohol is produced in earth containing organic matter 

 in decomposition, and hence it extends into the waters of 

 streams, and into the atmosphere. Still, the portions are so 

 infinitesimal that a water-drinker will never feel himself 

 "alcoholized;" the dose of alcohol contained in a cubic 

 metre of water (1000 litres), being at the most a gramme. — 



Elastic Restoration of Caoutchouc. — Objects made 

 of this substance easily lose their elasticity. Dr. Pol, 

 however, avers that their elasticity may be restored by 

 plunging them for an hour into a mixture composed of 2 

 parts of water and 1 part of ordinary ammoniac. 



