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SCIENCE 



[N. S. Vol. XXVI. No. 656 



whose record has been given, where, for the 

 five days beginning with April 3 and ending 

 with April 7, eight eggs were laid. 



There are two other instances where an 

 average of more than one egg in a day for a 

 limited period was made. In both of these 

 cases the possible mistake in the reading of 

 the numbers on the bands is to be considered, 

 as the hens had no other distinguishing mark. 

 The records for the particular period for each 

 of these hens follow. 



HEN STO. 27. JUNE, 1906 



There are eight other instances recorded 

 where hens laid two eggs in a day but in all 

 of these cases on either the day previous or 

 succeeding the day on which two eggs were 

 laid, no egg was laid. 



It should be distinctly understood that these 

 were not double yolked eggs, which are not 

 uncommon. Usually one egg was delivered in 

 the morning and the other in the afternoon. 

 In all of the recorded cases, the eggs were of 

 normal size and shape and in most cases they 

 were tested and found fertile. 



It is worthy of notice, but not necessarily 

 significant, that the single pullet hatched 

 last year from an egg laid by the hen whose 

 record is first given, did not make an ordi- 

 narily good record this year. 



GiLMAN A. Drew 



Univeksitt of Maine, 

 Okono, Maine 



on the origin of limestone sink-holes 

 The following are some of the statements 

 found in texts and other books relating to 

 sink-holes and their origin: 



1. It is for this reason [solution] too that 

 Limestone districts abound with funnel-shaped 

 cavities, descending from the surface verti- 

 cally into the rock, into which water sinks and 



disappears. They are often called swaUow- 

 holes or swallows. Wherever there was any 

 little despression in which water could lodge, 

 the bottom was eaten away lower and lower, 

 and a pipe formed at last leading from the 

 surface into the undeground channel. (" Phys- 

 ical Geology," Part I., by A. H. Green, p. 

 191.) 



2. In regions of soluble rocks, as we have 

 seen, many inequalities of the surface are 

 brought about by the chemical and me- 

 chanical action of underground water. Most 

 frequently the depressions caused by the col- 

 lapse of subterranean galleries and caves con- 

 tain no water. (" Earth Sculpture," by James 

 Geikie, p. 282.) 



3. In limestone regions the solvent action of 

 water has frequently gone on so extensively as 

 to leave its imprint upon the topographic 

 features of the landscape. . . . Entire land- 

 scapes are undulating through the abundance 

 of sink-holes — shallow depressions down 

 through which water has percolated and 

 escaped into the underground passages. 

 ("Rocks, Rock-Weathering and Soils," by 

 Geo. P. Merrill, p. 259.) 



4. From the surface sink-holes and pipes 

 are dissolved downward, while in the mass of 

 rock caverns are dissolved out, often, as in 

 the Mammoth Cave of Kentucky, many miles 

 in extent and with rivers of considerable size 

 flowing in them. (" An Introduction to Geol- 

 ogy," by William B. Scott, p. 89.) 



5. It has been estimated that there are in 

 Kentucky 100,000 miles of subterranean chan- 

 nels sufficiently large to permit the passage 

 of a man. Many " sinks " are found on the 

 surface, due to subsidence. (" A Text-Book 

 of Geology," by Albert Perry Brigham, p. 87.) 



6. When a considerable area has thus been 

 undermined, the upper rocks may cave in, 

 thus letting down the surface of the land 

 above. Many small lakes in Kentucky occupy 

 such sink holes. (" An Introduction to Phys- 

 ical Geography," by Gilbert and Brigham, 

 p. 99.) 



7. Thus across the limestone upland of cen- 

 tral Kentucky one meets but three surface 

 streams in a hundred miles. Between their 

 valleys surface water finds its way under- 



