166 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



preserved, and that in all probability human bones are much 

 less permanent in their structure than those of many other 

 animals. He cites experiments by Dr. Lindley, in which one 

 hundred and seventy-seven specimens of plants, belonging to 

 different natural orders, including those which are constantly 

 present as fossils in the coal measures, and those also which 

 are universally absent, were placed in water in a tank and 

 left for two years untouched water being simply poured in 

 to replace that which was wasted by evaporation. At the 

 end of that time it was found that certain kinds had entirely 

 disappeared, while others had left some more or less recog- 

 nizable traces ; and again others, especially fungi, ferns, and 

 coniferous trees, precisely those which are generally found 

 fossilized, were comparatively well preserved. 



He also remarks, in regard to the mollusca, that certain 

 shells, like oysters and limpets, are found more frequently 

 than others, such as cockles, this seeming to be a curious 

 fact, the material of both being the same, namely, carbonate 

 of lime and animal matter. It has, however, been shown 

 that, under certain conditions, the carbonate of lime in lim- 

 pets and oysters assumed the form of calcite, while in cockle- 

 shells and their allies it took the form of arragonite, the mole- 

 cules of the latter form being in much less stable equilibrium 

 than those of the former, and consequently much more liable 

 to disappear under unfavorable circumstances. 



As an instance, showing the readiness with which human 

 bones disappear, Mr. Pengelly cites the fact that the Dutch 

 government in 1853 drained off the Haarlem Lake, on which 

 there had been many shipwrecks and naval fights, and where 

 thousands had found a watery grave. The canals and trenches 

 dug to a considerable depth through the rescued land must 

 have had an aggregate length of thousands of miles, and yet 

 not a sinsrle human bone was exhumed from first to last. 

 Some weapons and a few coins, and one or two wrecked ves- 

 sels, alone rewarded the antiquaries who watched the opera- 

 tions with the hope of a rich harvest. Here, as in cavern 

 deposits and river gravels generally, works of art alone fur- 

 nished evidence of the existence of man, even though no part 

 of the deposit could be more than three hundred years old, 

 as the lake was formed by an inundation toward the end of 

 the sixteenth century. 16 A,Jidy, 1871, 327. 



