GS Intelligence and Miscellaneous Articles. 



maline crystals for beat and electricity. Dr. Lodge had shown 

 that an . explanation of pyroelectricity might be given if such crys- 

 tals possessed a unilateral conductivity for electricity. A body is 

 said to possess unilateral conductivity for any thing if it conducts 

 better in one direction than in the opposite one — as, for example, 

 a tube with a series of funnels in it all turned the same way for 

 fluids, and apparently, in the case of Greissler's tubes, for electricity 

 also. The result of their experiments was that tourmaline crystals 

 do possess a unilateral conductivity for heat as long as their tempe- 

 rature is variable, and similarly for electricity as long as the tempe- 

 rature varies. The first of these facts is an important and valuable 

 increase of our knowledge ; but the latter, as they point out, is of 

 course only due to the already known electromotive force which 

 constitutes their pyroelectric properties. They seem to have been 

 dissatisfied with these results ; for they had hoped to discover uni- 

 lateral electric conductivity independently of changes of tempera- 

 ture. They do not seem to have noticed that what analogy should 

 have led them to look for was unilateral conductivity during changes 

 of intensity of the current. It is to be hoped that, as they possess a 

 very fine specimen of tourmaline, they will continue their investi- 

 gations into this point. In the meanwhile it may be worth noticing 

 a mechanical illustration of how this might be connected with pyro- 

 electricity. Suppose a wire carrying a current, surrounded by a 

 number of magnets, and that a majority of them pointed in one 

 direction round the wire, and that each was kept in its place by a 

 spring. On passing a current through the wire, all the magnets 

 that did not point round it in a particular direction would tend to 

 set themselves in this direction; and during changes of intensity of 

 the current, work would be done against or by the springs. If the 

 current passed in such a direction that the majority of the magnets 

 were set so as to remain unchanged, there would be less work done 

 by changes of intensity than if the current were in the opposite 

 direction ; and this would give rise to an apparent unilateral con- 

 ductivity. I say " apparent," because the weakening of the current 

 is due to an inverse electromotive force, and not to a true increase 

 of the resistance. The same effect would be produced by supposing 

 a majority of the magnets turned in the same direction along the 

 magnet, and kept in position by two springs, one on each side, but 

 one stronger than the other, when of course a current would have 

 to do more work in turning them to one side than to the other, so 

 that in this case also there would be apparent unilateral conducti- 

 vity during variations of the current. 



jSTow, suppose that the proportion of polarized magnets or their 

 strength depended on the temperature of the system. It is then 

 evident that during changes of temperature there would be changes 

 in the numbers or strengths of the polarized magnets : either would 

 produce an electromotive force in the wire during the change. 

 Hence the phenomena of pyroelectricity would be manifested by 

 such a system. I put these forward merely as illustrations, not 



