262 



SCIENCE. 



[Vol.. XI. No. 2 78 



known, an entirely satisfactory plan of prevention cannot be pro- 

 posed. At present, watering from troughs instead of from prairie 

 pools, pasturing the lambs on prairie not recently pastured on by 

 older sheep, and, after weaning, removing them to fresh pastures, 

 are recommended. The practice of winter feeding on grain and hay 

 undertaken by ranchmen is especially advisable in keeping up the 

 health of infected animals. 



different, the latter being 

 interesting: — 



Iv higher. The following table is 



ELECTRICAL SCIENCE. 



Long-Distance Telephone-Lines. 



It is known that there is considerable difficulty in transmitting 

 speech by telephones over long distances, unless special precautions 

 are taken in the construction of the Imes. Dr. Wietlisbach has 

 investigated the best conditions for telephone-lines, and has arrived 

 at the following laws for the effect of the disturbing causes : — 



1. The greater the resistance and leakage, the smaller is the 

 strength of the received current. 



2. Self-induction favors high notes. 



3. Capacity favors low notes. 



4. The resistance diminishes the effect of self-induction, and in- 

 creases the effect of capacity. 



5. Leakage diminishes the effect of capacity, and increases that 

 of self-induction. 



6. In a conductor having both self-induction and capacity, the 

 relative intensity of the undulations increases and decreases peri- 

 odically with the rise in the height of the note. 



7. The magnetic permeability and the polarization of the con- 

 ductor destroy the clearness of the transmission. 



If all of the factors remained constant, it would be possible to 

 design a line in which the relations between capacity, self-induc- 

 tion, resistance, etc., were such that all notes would be transmitted 

 with equal clearness. For example : in a submarine cable where 

 the capacity is great, a man's voice is heard farther and more dis- 

 tinctly than a woman's, since capacity favors low notes as compared 

 with high notes ; but it would be possible to so increase the self- 

 induction of the line that both would be heard with equal distinct- 

 ness, and at the same time both would be more perfectly repro- 

 duced, since all of the tones would be given their proper relative 

 values. 



Unfortunately this cannot be readily done in practice, since the 

 leakage, which diminishes the effect of capacity and increases that 

 of self-induction, is in most lines a quantity which varies with the 

 state of the weather. Dr. Wietlisbach thinks, therefore, that the 

 best way to build a line is to make all of the effects as small as 

 possible, using a looped circuit of copper wire of low resistance and 

 capacity. The empirical rule used in practice is to make the prod- 

 uct of the resistance and capacity of any line less than a certain 

 constant which has been determined by experiment. One would 

 suppose, however, that, by roughly adjusting the capacity and self- 

 induction of the line, much clearer speech would result. 



Possibilities and Limitations of Chemical Genera- 

 tors OF Electricity. — Mr. Francis B. Crocker read a paper 

 before the American Institute of Electrical Engineers with the 

 above title, which cannot fail to be of interest at the present time ; 

 more especially as primary-battery schemes seem about to invade 

 this country from what has been until now their home, England. 

 Mr. Crocker first gives the ordinary formula for calculating the 

 electro-motive force from the energy of chemical combinations that 

 go on, — £■'= 4.16 aH, " where E is the electro-motive force, a 

 the electro-chemical equivalent (grams per coulomb), and 1/ is 

 the number of heat-units (gram-degrees) produced per gram of 

 material by the given combination." It should be pointed out here 

 that this formula is slightly inaccurate, as has been shown by Wil- 

 lard Gibbs and Helmholtz. Gibbs gives it as (putting in the 



To-T 

 above form) E = 4.16 aH , where T is the temperature of 



dissociation, and T the temperature of the cell. We would expect, 

 then, that the electro-motive forces obtained from experiment, and 

 those calculated from the uncorrected formula, would be slightly 



Combining wi 

 Chlorine. 



Calcu- 

 lated, 



Deter, 

 mined. 



Magnesium , 3.24 



Zinc ' 2.og 



Cadmium 2. 00 



Aluminium ; 2,30 



Iron 1.75 



Cobalt 1.64 



Nickel 1-57 



Tin I 1. 71 



Lead I 1.76 



Copper I 1.40 



Antimony ] 1.30 



i 



Brom 



ne. 



lodi 





Calcu- 



Deter- 



Calcu- 



1 



lated. 



mined. 



lated. 





_ 



_ ' 



_ 





i.6i 



.•79<?)l 



I •OS 





I 58 



..58 1 



•97 



, 



1.70 



1-53 



I 00 



1 



1.50 



1.30 



85 





1.50 



I 30 



_ 





..38 



I -.13 



•85 





1.07 





.69 





•97 



•95 



•59 



' 



- 



- 



- 



.83 

 .64 



The table of costs is, however, really important, especially to in- 

 vestors. In the table there is given opposite each substance the 

 amount consumed and the cost for a horse-power hour. To find 

 the total cost of a cell, the sum of the costs of its constituents 

 should be taken. These cells all employ zinc as the positive ele- 

 ment. 



Zinc used with following Electro- o 

 Negative or Depolarizing Ele- ji 



Free iodine - . 



Free bromine - 



Free chlorine 



Free oxygen 



Free sulphur 



Cheviical Co}npoiinds. 



Water 



Nitric acid.. 



Chromic acid 



Copper sulphate (anhyd ) 



Iron perchloride 



Silver chloride 



Mercury sulphate 



Mixtures. 

 Potassium bichromate (3 parts) 1 

 Sulphuric acid (7 parts) ( 



Potassium bichromate (3 parts) \ 

 Sulphuric acid (4 parts) ) 



I2I ? 



6. S3 J22.97 



2 76 



'33 =5 



5 45 



In this table the products of the action are not taken into account. 

 In some cases these products would be of considerable value, as 



