724 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



breadth, and neatly hollowed out. If all " giant pots" are formed by the water, 

 as we believe at the present time, then this pot, situated so high above the water, 

 must doubtless be several thousand years old. 



At a time wlien the existence of the glacial period was unknown 



no other explanation than that given by Linne could be advanced, and 



especially remarkable is his emphasis upon the peculiar characteristic 



of these potholes, i. e., their vertical position even on a mountain slope. 



Nor should we forget what he says about the great age of the one last 



mentioned. 



******* 



* * * During the jfirst day of his journey to Skane (April 29, 

 1749), he records an occurrence of marl which must have been of 

 great importance at that time : 



Marl ("earth marrow") existed in larger quantities in the neighborhood of 

 Upsala than in any other place, a fact which to a great extent contributed to the 

 fertility of these fields, * * * By the use of marl or " earth mai'row," as 

 some call it, the English and French have brought their cultivated fields up to 

 a high standard of productivity, for which reason our nation, during the last 

 years, and especially since we began to pay more careful attention to agricul- 

 ture, has been anxious to ascertain whether such a useful soil could not be 

 found at home. We therefore secured samples of marl from England, France, 

 and the Netherlands, but because of variations in color and composition it was 

 difficult to find a method of distinguishing the marl, until it was noticed a year 

 ago that all marl seemed to ferment in contact with sour liquids, such as vine- 

 gar, diluted nitric acid, and other such fluids. Hence the conclusion was arrived 

 at that marl was nothing else than a lime clay or chalk clay, and only a bleach- 

 ing or leavening soil which has retained its ability to break up the alkalinity 

 of the ground, which is unhealthy to plants * * *. From the foregoing a 

 farmer may now readily detect true marl, because a clay which is mixed with 

 marl will effervesce if a few drops of aqua fortis be poured over it. If the same 

 clay effervesces in the presence of vinegar, however, the marl is still better, 

 because many a clay that contains but little marl and which will ferment when 

 mixed with aqua fortis will not ferment when mixed with vinegar alone. 



* * * In another place in the description of the same journey 

 Linne states that it was " the vice-president, Baron S. C. Bjelke," 

 who in 1748 first discovered this manner of detecting lime-bearing 

 clay or marl. 



Linne applied this experience during his travels in Skane. He 

 dwells upon the barrenness of the country around Asum, Koping, and 

 Maltesholm, south and southwest of Christianstad. * * * Sub- 

 sequently he emphasized the good results which might be obtained by 

 mixing the sandy soil with marl, and proposed that about half an acre 

 be marled by way of experiment. 



If this theory be confirmed by experience, opportunity will thus be afforded to 

 transform this entire sterile plain into the most magnificent soil, with incredible 

 advantage to the farmer and the country. 



