Chemistry and Physics. 99 



depends only on the sensitiveness of the instrument to changes in 

 R + r / and in the arrangement used in our experiments, the elec- 

 trodynamometer was sensitive to changes of about 1 part in 

 10,000 in JR + r. Therefore the construction of standard self- 

 inductances that will agree with each other to within 1 part in 

 10,000 is feasible by this method. 



9. Some Notes on the Zeeman Effect ; by J. S. Ames, R. F. 

 Earhaet and H. M. Reese. (From the Johns Hopkins Univer- 

 sity Circulars, No. 135.) — In our investigation of the effect of the 

 magnetic field on radiations in the ether, we have been led to 

 study certain variations from the phenomena discovered by Zee- 

 man, which seem to be worthy of note. Up to the present we 

 have studied the effect of a magnetic field upon the spark-spectra 

 of magnesium, iron, cadmium and zinc. The research is by no 

 means complete, but having discovered several new effects we 

 think it well to publish them at present, and to defer until later a 

 full discussion of the phenomena. 



Our apparatus has been the small concave grating of the Physi- 

 cal Laboratory, which has a radius of curvature of about eleven 

 feet. The grating is ruled with 15,000 lines to the inch and is 

 five inches in width. The magnetic field has been produced by 

 an ordinary form of electro-magnet, but we have made no at- 

 tempt to measure the intensity of the field, because our object 

 has not been to establish numerial relations. The field, however, 

 was strong enough to produce a separation in the case of iron of 

 about a tenth of an Angstrom unit, and the definition has been 

 most satisfactory. The method of use was to introduce between 

 the spark and the slit a Nicol's prism and quartz lens, and to 

 photograph the resulting spectra along the middle of the photo- 

 graphic plate, then turning the Nicol's prism through 90°, and at 

 the same time turning a shutter which is placed in front of the 

 photographic plate, to expose the two edges of the plate to the 

 new radiation coming through the Nicol's prism. By this method 

 we secure on the same plate the components of the vibrations 

 polarized along the lines of force aud at right angles to them. 



We have studied the effect of the magnetic field upon the iron 

 spectrum from wave-length 3400 tenth meters to wave-length 

 4300, and in this region have noticed that all the lines, with cer- 

 tain exceptions to be noted, are influenced in the way discovered 

 by Zeeman. In particular, when the radiation at right angles to 

 the magnetic field is studied, each line in the spectrum is broken 

 up into three, the central component being plane polarized, with 

 its vibrations along the lines of force ; the two side components 

 being plane polarized at right angles to this, their vibrations being 

 at right angles to the field of force. 



We have observed, however, that three lines, of wave-length 

 3587' 13, 3733*4 7 and 3S65'G7, are affected in the opposite way ; 

 that is, the Hue is a triplet when viewed at right angles to the 

 magnetic field, but the central component is so polarized that its 

 vibrations are at right angles to the field, and the two side com- 

 ponents have their vibrations along the field. 



