238 



SCIENCE. 



[Vol. XI. No. 276 



Elongation and Contraction of Metals in Magnetic 

 Fields. — The first experiments made by Joule on the effect of 

 magnetization on the length of iron showed that the iron always 

 elongated. Mr. Bidwell has investigated the effects of very much 

 more intense magnetic forces than were used by Joule. At first 

 the iron expanded, but, after reaching a magnetic force of about 90 

 C.G.S. units, the iron began to contract, reaching its original length 

 at about 280 C.G.S. units, and contracting continuously until the 

 force reached 800 C.G.S. units, the limit of the experiment. Cobalt, 

 nickel, manganese, steel, and bismuth were also experimented on. 

 The two latter were practically uninfluenced in length by the appli- 

 cation of any magnetic force. Nickel and cobalt began to contract 

 from the first : nickel continued to contract to the limit of the ex- 

 periment ; cobalt contracted until the value of the force was about 

 400 C.G.S. units, when it expanded again ; not, however, reaching its 

 original value at a force of 800 C.G.S. units. 



A New Altbrnating-Current Electro-Motor. — Patents 

 have recently been issued to Nickola Tesla for an alternating-cur- 

 rent transformer and a motor which embody some novel features. 

 The motor is especially interesting : it is really a modification of a 

 plan proposed by Prof. Elihu Thomson, although the arrangement 

 is different. The armature consists of two coils wound at right 

 angles to each other on an iron core. The coils are short-circuited 

 on themselves, and are not in any way connected with the external cir- 

 cuit of the dynamo supplying the current. The field-magnet consists 

 of an iron ring, the four quadrants being wound with coils, of which 

 the two opposite are connected. The dynamo used to supply the 

 currents has two sets of coils, giving alternating currents of exactly 

 opposite phases. These currents are taken to the motor by sepa- 

 rate circuits, and are connected to alternate quadrants of the field- 

 magnet. The action of the motor consists in inducing, liy the alter- 

 nating currents in the field, currents in the closed circuit armature 

 coils, and in alternately attracting and repelling the coils. This 

 motor, then, has no commutator nor brushes, and, if it works, will 

 be the simplest possible means of transforming energy. As to the 

 efficiency and output of this motor, we will have more to say later. 



Heating Effect of Electric Currents. — M. Cailletet has 

 experimented on the heating of wires by an electric current when 

 the pressure of the air around the wire is increased. He finds that 

 the heating effect is decreased as the pressure increases. A cur- 

 rent that would fuse a wire under ordinary pressures, will only raise 

 it to a dull redness when the pressure is increased. This shows 

 the importance of convection in incandescent lamps, and the desir- 

 ability of the highest attainable vacuum. 



Variation of Co-efficients of Induction. — Mr. W. E, 

 Sumpner has experimented on the co-efficients of self-induction of 

 transformers under various conditions. He finds that the co-effi- 

 cient varies greatly with different conditions of current, etc., and 

 plots curves representing the values for different currents, defining 

 the co-efficient as the rate at which magnetism changes with the 

 current. The results of Mr. Sumpner's work show, perhaps, for 

 the first time, the very great variation in a co-efficient that has been 

 taken as constant in a large number of solutions of problems bear- 

 ing on the subject of alternating currents. In this connection a 

 series of papers on induction-coils, that is now being published in 

 the Electrical World, is important. Heretofore the subject of al- 

 ternating currents has not been experimented upon in a way to 

 show whether the assumptions that have been made are approxi- 

 mately correct. These ' Experiments on Induction-Coils ' show that 

 many of the solutions that have been given are altogether wrong. 

 So far, however, the most important papers of the series have not 

 been published : their appearance is awaited with interest. 



New Method of reading Reflecting-Instruments. — 

 The following is an abstract from a paper by M. F. Drouin, in the 

 Lumiere Eleciriquc : " The usual mirror is replaced by a thin disk 

 of glass. The scale being behind the instrument, the observer in 

 front sees the scale directly through the glass; while he sees re- 

 flected from the front surface of the glass the image of an object, 

 such as a black line on a white background, placed in front of the 

 instrument and to one side. When the glass disk is deflected 

 through an angle a, the virtual image of the mark is displaced 



through a distance d. tan 2a (d=distance from glass to scale). 

 The method can be used in a well-lighted room, and does away 

 with all the trouble of lamps and shades." 



BOOK-REVIEWS. 



Tenih Annual Report of the Connecticut State Board of Health 

 for the Year ending XoTci. i, i2i%7,with the Registration Re- 

 port for 1886. New Haven, State. 



In addition to the usual official reports and tables of vital statis- 

 tics, this volume contains a report on river-pollution by Prof. S. W. 

 Williston, M.D., Ph.D., with reports on water-analyses by Prof. 

 H. E. Smith, M.D., and William G. Daggett, M.D. This report is 

 a very valuable and thorough one, and covers nearly one hundred 

 pages. It is the outcome of an act of the Legislature authorizing 

 the State board to investigate and ascertain, as far as practicable, 

 all facts in relation to the pollution of streams and natural waters 

 of the State by artificial causes, in order to determine the sanitary 

 and economic effects of such pollution. In the report are described 

 the chemical processes employed in the manufacture of brass, iron, 

 paper, woollen, cotton, and silk goods, hats, and rubber goods, and 

 the impurities which are cast into the streams of the State from 

 these manufactories. In the analyses of the water, both the biologi- 

 cal and chemical methods vyere employed. 



The annual report also contains reports on an epidemic of dysen- 

 tery in Thomaston, by R. S. Goodwin, M.D. In this report the 

 author presents the following conclusions as a result of his study of 

 the epidemic : " that the outbreak of dysentery at Thomaston, 

 and at every other town on the Naugatuck River, occurred in 

 consequence of the co-operation of several favorable influences. 

 These were a certain season, a certain high temperature, a certain 

 favorable location, unsanitary modes of living, and the use of im- 

 pure drinking-water. Nevertheless, infection with a certain spe- 

 cific poison was the sole cause of this disease, and the role played 

 by these influences in its etiology was only to irWrease the predis- 

 position to the affection by rendering the human organism more 

 sensitive to the action of this unknown poison." 



Dr. C. W. S. Frost contributes a sanitary report of the city of 

 Waterbury, from which it appears that small-pox, diphtheria, 

 measles, and dysentery prevailed during the year. 



Dr. F. E. Beckwith has contributed remarks on the recent out- 

 break of typhoid or enteric fever at Southampton, L.I. Just why 

 this report is printed in the ' Annual Report of the Connecticut 

 State Board of Health,' does not appear, unless the explanation is 

 to be found in the following paragraph : " The sanitary suggestions 

 which close the paper apply not only to Southampton, but to every 

 small seaside resort in a developing state, where there are similar 

 conditions of soil, surface of country, and water-supply." The re- 

 marks are instructive and to the point, and are worthy a place in 

 the report. 



Eleventh Annual Report of the Board of Health of the State of 

 New Jersey, and Report of the Bureau of \'ital Statistics. 

 1887. Trenton, State. 



In this report are the following papers : ' The Legal Aspect o f 

 the Pollution of Streams,' by E. S. Atwater; ' .Wr, Water, and Food,' 

 by Ezra M. Hunt, M.D. ; ' Outlines of Representative Sewer Sys- 

 tems,' by J. J. Croes, C.E., F. S. Odell, C.E., George P. Olcott, C.E.. 

 C. P. Bassett, C.E., and Charles McMillan, C.E. ; ' Exposure and 

 Diseases of Operatives,' by D. Warman, M.D. ; ' Typhoid-Fever at 

 Mount Holly,' by E. M. Hunt, M.D. ; abstracts from papers and 

 discussions of the New Jersey Sanitary Association ; ' Report on 

 the Water-Supply from the Passaic Watershed,' by Prof. A. R. 

 Leeds, Ph.D. ; and reports from the health-inspectors. The board's 

 report also contains a list of persons practising medicine in the 

 State. 



In his paper on air, water, and food. Dr. Hunt discusses the in- 

 fluence of impure air on the death-rate, and refers to the investiga- 

 tions of this subject by Messrs. Carnelly and Haldane of University 

 College, Dundee ; and also those of Dr. Anderson, the health-officer 

 of that city. Several experiments showed that the average of car- 

 bonic acid and organic matter was uniformly higher in town than 

 in suburban or country air, and that in open places the carbonic acid 



