October 5, 1917] 



SCIENCE 



343 



ments adapted to sea-conditions, for establish- 

 ing a practicable and suitable routine of ob- 

 serving and of checking instruments and in 

 general for learning how to make magnetic ob- 

 servations at sea far more accurately and 

 systematically than had ever before been at- 

 tempted. 



The " magnetic constants " of this wooden 

 sailing vessel were smaller than those of any 

 vessel which had been previously used for mag- 

 netic observations; but, small as they were, 

 they necessitated many corrections and fre- 

 quent " swinging the ship " to obtain the ac- 

 curacy which Dr. Bauer had determined upon 

 as the goal to be attained. This not ohly con- 

 sumed much time, but also diminished the pre- 

 cision of the final results. Accordingly, the 

 non-magnetic yacht Carnegie was built in 

 1909 in which the use of iron was almost 

 wholly avoided; wooden pins, and bolts of 

 copper and of Tobin bronze took the place of 

 iron nails, the producer gas engine used for 

 auxiliary power was constructed of bronze, 

 and the only magnetic materials used were the 

 steel valves, piston rings and cam-rollers. Re- 

 peated tests have shown that this imique ves- 

 sel has no appreciable eiiect upon the instru- 

 ments; and in her various cruises aggregating 

 more than 160,000 miles, observations have 

 been obtained with comparative ease and ra- 

 pidity whose accuracy is far beyond anything 

 which had previously been possible at sea. 



The first 154 pages of the present volume 

 give an account of the work done on the 

 Galilee, while the remainder deals in the same 

 way with the observations made on the Car- 

 negie. The various instruments are fully de- 

 scribed and illustrated, and it is most interest- 

 ing to follow their gradual improvement and 

 perfection. To the experimental physicist this 

 is one of the most attractive portions of the 

 report; especial mention may be made of the 

 beautiful and ingenious marine earth-inductor 

 described on pp. 196 et seq. A full account is 

 given of the methods of making observations, 

 their reduction and correction and of the sys- 

 tem of checks and controls between the various 

 instruments, as well as those introduced by 

 shore observations which were made at every 



opportunity. The final results for each cruise 

 are given in tabular form and no detail is 

 omitted which might add to their usefulness. 



In addition to the magnetic measurements, 

 systematic observations were also carried out 

 on atmospheric electricity, ionization and 

 radio-activity; these form the subjects of the 

 special reports with which the volume closes. 



The practical utility of this great series of 

 magnetic observations in correcting mariners' 

 charts of magnetic variation is obvious; seri- 

 ous errors in the present charts have been 

 found and their correction lessens the dangers 

 of navigation in times of storm and fog when 

 astronomical observations are impossible. 

 And quite apart from this most useful result 

 the ultimate scientific value of such a survey 

 continued year after year, as it will doubtless 

 be when the war is over, is very great. The 

 earth's magnetism is one of the great myste- 

 ries of physical and cosmical science; observa- 

 tions on land alone cover too small an area of 

 the earth's surface to afford an adequate basis 

 of knowledge of the earth's field and of the 

 intricacies of its secular variations. Con- 

 tinued, systematic sea observations of the 

 accuracy of those recorded in this report form 

 a necessary stage in the solution of the great 

 problem; when that is obtained it will doubt- 

 less lead to a further knowledge of the sun's 

 magnetism and may well have results of the 

 highest significance in cosmical theory. 



This volume is a monument to the well- 

 directed enthusiasm and foresight of Dr. Bauer 

 and to the skill and zeal of his associates. In 

 this case as in many others the Carnegie In- 

 stitution deserves the thanks of the scientific 

 world for generously supporting and wisely 

 forwarding work which could scarcely have 

 been done at present by any other agency. 



H. A. BUMSTEAD 



Yale IJNrvERsiTT 



THE RELATION OF THE MALPIGHIAN 

 TUBULES OF THE HIND INTES- 

 TINE IN THE HONEYBEE 

 LARVA 



It has been known for nearly a hundred 

 years that the mid-intestine of larvre of bees 



