Astronomy and Terrestrial Physics. 163 



coast of Northumberland. His method of investigation was like 

 that of Darwin on earthworms. His results show that while the 

 earthworms studied by Darwin brought to the surface in four 

 cases 14*58, 18'12, 7*56 and 15-1 tons per acre annually, the Lob- 

 worms bring up 136 times this amount in the same time. In his 

 six trials he obtained per acre 901, 3146, 3147, 449, 396, 329 tons 

 per acre. The average is 47,237 cubic feet annually per acre ; 

 which corresponds, after drying and pressing, to a layer 13 inches 

 thick. The Lobworms burrow to a depth of 1 2 to 24 inches ; 

 and taking the higher figure, "the layer of sand in which they 

 live must on an average pass through their bodies once in 22 

 months." Fresh sand is being continually placed by them within 

 the wearing action of the sea. The surface over which they 

 occur is inclined ; and at the touch of the water, the casting sinks 

 down and swells out at the base, more of it flowing down the 

 slope than up. It thus loses its vermiform appearance and is 

 changed to a low mound elongated downward or completely 

 flattened out. 



IV. Astronomy and Terrestrial Physics. 



1. Periodic Variation of Latitude. — .The observations of Dr. 

 Kiistner at the Berlin Observatory, published in 1888, indicated 

 the surprising phenomenon of the variation of the geographical 

 latitude of Berlin, to the extent of nearly, if not quite, half a 

 second. This announcement was received by astronomers with 

 considerable hesitation, and only the known accuracy of the 

 methods of the Berlin Observatory, together with the established 

 high reputation of the observer, secured for it the careful atten- 

 tion which its apparent improbability might otherwise have pre- 

 vented. Various explanations were suggested : among them 

 some possible difference between the atmospheric refraction north 

 and south of the zenith : also, since the variation seemed to be an 

 annual one, some influence connected with the changes of the 

 seasons: also some imaginable systematic errors in the declina- 

 tions of the stars employed, varying with their right-ascensions. 



The International Geodetic Association deputed Prof Helmert, 

 director of its Central Bureau, to arrange for concurrent action 

 by various observatories for investigating the nature of the varia- 

 tions in question, a plan which was effectively carried out. An 

 elaborate collection and discussion of more than 5000 latitude 

 determinations was presented by Dr. Albrecht to the Association. 

 The simultaneous observations at Prague and • Potsdam gave 

 results in perfect conformity with those made at Berlin, and it 

 soon became manifest that the phenomenon was no local one, but 

 that all the latitude-determinations at the several places gave 

 accordant indications of simultaneous fluctuations in 1889 ex- 

 ceeding the half of a second. Later the hypothesis that the 

 pei'iod of the variation was annual was disposed of by evidence 

 that the various latitudes determined in 1890 were in general 



