SCIENCE 



[Vol. XVllI. No. 440 



soucdings down to thirty fathoms, and the other slung so as to 

 register down to forty-five fathoms. With the former about four 

 and a half horse-power is absorbed at a speed of eight knots. It 

 should be stated that the apparatus can be used for taking sound- 

 ings at any depth within its limits of working, as well as to form 

 a permanent indication of when the ship passed into water of less 

 than a given depth. All that is required to do is to pay the kite 

 out slowly, with a hand on the brake which is provided for check- 

 ing the speed. When the gong sounds, a glance at the dial will 

 show the vertical depth due to the length of wire paid out. 



EXPERIMENTS WITH LEYDEN JARS. 



At a meeting of the Physical Society, London, held June 13 

 (reported in Engineering of June 19), some experiments with 

 Leyden jars were shown by Dr. Lodge. The first one was with 

 resonant jars, in which the discharge of one jar precipitated the 

 overflow of another when the lengths of the jar circuits were 

 properly adjusted or tuned. The latter jar was entirely discon- 

 nected from the former, and was influenced merely by electro- 

 magnetic waves emanating from the discharging circuit. Length- 

 ening or shortening either circuit prevented the overflow. Correct 

 tuning was, he said, of great importance in (hese experiments, for 

 a dozen or more oscillations occurred before the discharge ceased. 

 The eflfect could be shown over considerable distances. In con- 

 nection with this subject Mr. Blakesley had called his attention to 

 an observation made by Priestley many years ago, who noticed 

 that when several jars were being charged from the same prime 

 conductor, if one of them discharged, the others would sometimes 

 also discharge, although they were not fully charged. This he. 

 Dr. Lodge, thought might be due to the same kind of influence 

 which he had just shown to exist. The word " resonance," he 

 said, was often misunderstood by supposing it always had refer- 

 ence to sound, and as substitutes he thought that "' symphoning" 

 or " symphonic " might be allowable. 



The next experiment was to show that wires might be tuned to 

 respond to the oscillation of a j^r discharge, just as a string could 

 be tuned to respond to a tuning-fork. A thin stretched wire w;as 

 connected to the knob of a jar, and another parallel one to its 

 outer coating, and, by varying the length of an independent dis- 

 charging circuit, a glow was caused to appear along the remote 

 halves of the stretched wires at each discharge. Each of the wires 

 thus acted like a stopped organ pipe, the remote ends being the 

 notes at which the variations of pressure are greatest. By using 

 long wires he had observed a glow on portions of them with the 

 intermediate parts dark: this corresponded with the first harmonic, 

 and by measuring the distance between two nodes, he had deter- 

 mined the wave length of the oscillations. The length so found 

 did not agree very closely with the calculated length, and the dis- 

 crepancy he thought due to the specific inductive capacity of the 

 glass not being the same for such rapidly alternating pressures as 

 for steady ones. He also showed that the electric pulses passing 

 along a wire could be caused (by tuning) to react on the jar to 

 which it was connected, and cause it to overflow, even when the 

 distance from the outside to the inside coating was about eight 

 inches. During tliis e.x;periment he pointed out that the noise of 

 the spark was greatly reduced by increasing the length of tbe dis- 

 charging circuit. The same fact was also illustrated by causing 

 two jars to discharge into each other, spark gaps being put both 

 between their inner and outer coatings, so as to obtain "A" 

 sparks and "B" sparks. By putting on a long "alternative 

 path " as a shunt to the B spark gap, and increasing that gap, the 

 noise of the A spark was greatly reduced. He had reason to be- 

 lieve that the B spark was a quarter phase behind the A spark, 

 but the experimental proof had not been completed. 



He next described some experiments on the screening of electro- 

 magnetic radiation, in which a Hertz resonator was surrounded 

 by diflierent materials. He had found no trace of opacity in in- 

 sulators, but the thinnest film of metal procurable completely 

 screened the resonator. Cardboard rubbed with plumbago also 

 acted like a nearly perfect screen. In connection with reso- 

 nators he exhibited what he called a graduated electric eye, or an 

 electric harp, made by his assistant, Mr. Robinson, in which strips 



of tinfoil of different lengths are attached to a glass plate, and 

 have spark gaps at each end which separate them from other 

 pieces of foil. One or other of the strips would respond accord- 

 ing to the frequency of the electro-magnetic radiation falling 

 upon it. 



A GIFT TO THE UNIVERSITY OF CHICAGO. 



The executors of the estate of the late William B. Ogden, who 

 was the first mayor of Chicago, have selected the University of 

 Chicago as one of the beneficiaries under the terms of Mr. Ogden's 

 will, — giving it a scientific school. 



The conditions attached by the executors to the gift — which 

 will amount to from three hundred thousand to half a million 

 dollars — are, that the school shall be a separate department of 

 the university, and bear the name of the Ogden Scientific School, 

 its purpose being to furnish graduate students with the best facili- 

 ties possible for scientific investigation by courses of lectures and 

 laboratory practice. The income of the money appropriated is to 

 be devoted to and used for the payment of salaries and fellow- 

 ships, and the maintenance of laboratories in physics, chemistry, 

 biology, geology, and astronomy, with the subdivisions of these 

 departments. A large share of the time of the professors in the 

 school is to be given to original investigation, and encouragement 

 of various kinds is to be furnished them to publish the results of 

 their investigations, a portion of the funds being set apart for the 

 purpose of such publication. The school is to include all the 

 graduate work of the university on £he subjects mentioned, and 

 further appropriations or donations which may be made toward 

 these objects are to be added to the original foundation, and not 

 to be devoted to new schools doing similar or parallel work. 

 Some portion of the income of the foundation is to be set apart for 

 the purchase of books to be placed in the special departmental and 

 laboratory libraries of the proposed school. 



The university in accepting this gift is requu'ed to pledge itself 

 to erect the contemplated school, under the suggested name, on 

 the receipt of |300,000, whether or not the wish and expectations 

 of the trustees he realized in the final receipt from the fund of a 

 much larger sum. In the event, however, of any unforeseen cir- 

 cumstances preventing the money designated from reaching the 

 sum of $300,000, the money which mayxbe received shall be used 

 for th3 endowing of one or more professorships in the university 

 to be severally known as the Ogden Professorships. 



It is further desired that at least one of the board of trustees of 

 the university shall be the nominee of the executors and trustees 

 of Mr. Ogden's estate, in order that in the formation and develop- 

 ment of the scientific school proposed, the wishes of the trustees 

 may be voiced by at least one member of the governing board of 

 the university. And finally it is required that it shall be distinctly 

 understood that there shall be absolute freedom in respect to the 

 admission to the proposed school of students and professors alike, 

 without reference to their particular religious beliefs. 



LETTERS TO THE EDITOR. 



•** Con-espondents are requested to he as brief as possible. The writer^s name 

 is in all cases required as proof of good faith. 



On request, twenty copies of the number containing his communication will 

 be fu^rnished free to any correspondent. 



The editor will be glad to publish any queries consonant loith the character 

 of the journal. 



The Dissipation of Energy. 



In passing through a grove of scattered timber after a recent 

 thunder-storm, I came to a tree that had been struck by lightning, 

 a honey-locust (Gelditschia), about two feet in diameter. 



At the bifurcation of the topmost limbs the bark and sap-wood 

 were torn off for two or three inches in width, increasing as it 

 passed down, until within ten feet of the ground, where it seemed 

 to pass in and explode from the centre, splintering the tree on one 

 side for a foot or two, then tearing the bark and sap-wood for a 

 little ways down, and then leaving the rest without a mark on it 

 for two or three feet above the roots. The splinters were scattered 

 in a half circle twenty feet from the tree. The tree appeared to 

 be perfectly sound and free from defect. 



