Chemistry and Physics. 313 



prominences were in high latitudes, and another series of groups 

 of years, 1854-57, 1865-68, 1876-79, 1887-90, which are years 

 when prominences were less frequent in these regions.* 



The interesting conclusion to which Mr. Ellis arrived was that 

 "the excess of the equinoctial frequency over the solstitial fre- 

 quency is greater, the greater the degree of disturbance." 



This result thus helps to endorse the suggestion made in a 

 previous paragraph that the greater the disturbed solar polar 

 regions, the greater the difference between the magnetic fre- 

 quency at the equinoxes and solstices. 



Conclusions. — The conclusions arrived at in the above paper 

 may be briefly stated as follows : 



1. The seasonal variation in the frequency of magnetic storms 

 and aurorse depends on the position of the sun's axis in relation 

 to the earth. 



2. The epochs of the greatest inclinations of the sun's axis 

 towards or away from the earth, or in other words the greatest 

 exposure of the N. or S. solar polar regions to the earth during 

 a year, correspond to those of greatest magnetic and auroral 

 frequency. 



3. The epochs (groups of years), when the solar polar regions 

 are most disturbed, synchronize with those when the excess of 

 the equinoctial over the solstitial frequency of magnetic storms 

 is greatest. 



7. Physikalische Technik, oder Anleitung zu Experimental- 

 vortrdgen sowie zur Selbstherstellung einfacher Demonstrations- 

 apparate. Seventh Edition. By Dr. Otto Lehmann. Pp. 

 xx -f- 630. Braunschweig (Friedrich Vieweg und Sohn). — This 

 is the first part of volume one of Dr. Joseph Frick's well known 

 work. In this edition the book has been entirely rewritten and 

 very much enlarged. In its present form it is an exhaustive com- 

 pendium treating of the objects, methods and materials of the 

 experimental lecture as a branch of instruction in Physics. This 

 part of the work is concerned with the arrangement of the lecture 

 and preparation rooms and the workshop. All the details of the 

 installations for the electric, gas, water, steam, air pressure and 

 vacuum services and all the non-portable parts of the lecture- 

 room outfit are gone into with the greatest thoroughness. The 

 portion on the shop will be of value to the worker in the labora- 

 tory as well as to the lecturer. This part occupies nearly half 

 the book and contains numerous methods, recipes, etc., of use 



* The fact that continuous observation of solar prominences was only com- 

 menced in 1870 accounts for our lack of knowledge of the frequency of this 

 class of phenomena before that date. Since, however, during the last three 

 sunspot cycles it has been observed that polar prominences are most fre- 

 quent just a little after a sunspot minimum and up to and at the epoch of 

 the following sunspot maximum, it may be concluded that their appearance 

 previous to the year 1870 occurred at the same time in relation to the sun- 

 spot cycle. Ellis's groups of years previous to that date, namely, 1848-51 

 and 1858-61, may on these grounds be classed as years in which polar prom- 

 inences were present, whilst the groups 1854-57 and 1865-68 may be taken 

 as epochs when polar prominences were not so frequent. 



