738 



SCIENCE, 



[N. S. Vol. II. No. 



as far as Hungary was concerned, by Guido 

 Schenzl. On account of the slow, so-called secular 

 changes, whereby the distribution of terrestrial 

 magnetisna is forever changing its present as- 

 pect, it becomes essential to repeat such sur- 

 veys from time to time. We are thus enabled 

 to follow empirically, at least, the modus oper- 

 andi of that occult, elusive force — the cause of 

 the secular variation of terrestrial magnetism. 

 Other reasons make it desirable to repeat and 

 amplify former surveys. Not only are our 

 present methods of observations more refined, 

 but experience has repeatedly taught that a 

 magnetic chart based upon a few isolated obser- 

 vations gives but a very crude picture of the ac- 

 tual distribution of magnetism within the earth's 

 crust. The complexity of the picture or the 

 irregularity of the representative distribution 

 curves furnishes, generally speaking, the truest 

 index of the thoroughness of the underlying 

 survey. 



The first part of the report before us, of 

 which the second is to appear later, is devoted 

 to the publication and reduction of the obser- 

 vations made in Austria by Dr. Liznar, under 

 the auspices of the Vienna Academy of Sci- 

 ences. On pp. 230 and 231 is given in alphabe- 

 tical order the 109 observation stations, to- 

 gether with their geographical positions and the 

 observed magnetic elements reduced to the 

 epoch 1890.0. The intensities (horizontal and 

 total) are given to four decimals in mm. mg. s. 

 units — a simple division by 10 will reduce to 

 c. g. s. units. 



The discussion of the results and the deline- 

 ation by charts of the magnetic] distribution 

 are reserved for the second part, which is also 

 to contain the observations made by previous 

 agreement during the same time interval along 

 the Adriatic coast by the Hydrographic office of 

 Pola, and in Hungary by the Central Meteoro- 

 logical and Magnetic Institute of Budapest. 

 Great care was taken that observations thus 

 made imder different auspices should be strictly 

 comparable. Frequent inter-comparisions of 

 the instruments used were made by selecting 

 cotpmon observing stations, as also were the in- 

 struments compared with those at the Central 

 Institute. 



Two points are suggested by this report, the 



first of which may perhaps appear trivial, but 

 from which we, nevertheless, might draw a use- 

 ful lesson. This report, like many others of a 

 scientific character, received from abroad is 

 above all well printed, a fact which is not 

 characteristic of some of our scientific govern- 

 ment publications, whose typographical execu- 

 tion in several notable instances has been abom- 

 inable. We believe that what is worth doing at 

 all is not alone worth doing well, but also print- 

 ing well. Too often the character of the contents 

 is judged by the external appearance. 



The second point suggested is the great de- 

 sirability of a detailed magnetic survey of our 

 own confines. Our Coast and Geodetic Survey 

 is doing excellent work in this direction, but 

 the comparatively few observations, if you con- 

 sider the territorial extent involved, it can 

 make with all its manifold other duties, are 

 wholly inadequate for a fairly accurate repre- 

 sentation of terrestrial magnetic distribution in 

 the United States. How fraught with problems 

 of the most interesting and suggestive charac- 

 ter a detailed magnetic survey can present to 

 the physicist and to the geologist has been 

 clearly shown by the Riicker and Thorpe min- 

 ute magnetic survey of Great Britain. 



At the present time when many of the 

 European governments have either just carried 

 out detailed surveys or are about to do so, it be- 

 hooves us to fall in line. But one State of the 

 Union has received the distinction of having 

 a fairly complete magnetic survey made of 

 it, and this was due to the private enterprise 

 and enthusiasm of Prof. Francis E. Nipher, of 

 Washington University, St. Louis. Good work 

 has also been accomplished in this direction by 

 the geologists in New York, New Jersey and 

 Pennsylvania. It is firmly believed that more 

 of such detail work will redound to the bene- 

 fit of geology and of geomagnetism. 



L. A. B. 



Tables for the Determination of Common Minerals. 



By Prof. W. O. Crosby, of the Mass. Inst. 



of Technology. 



This book, the third edition of which has just 

 been published (1895), is a vei-y carefully pre- 

 pared scheme for the determination of about 

 two hundred and twenty-five of the more com- 



