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THE POPULAR SCIENCE MONTHLY. 



At Reikum the geysers have no deposits, and the " Great Geyser " at 

 Hankadal is situated on the summit of a broad and rather gently slop- 

 ing mound. Some of these differences will be rendered more apparent 

 when placed in a tabular form : 



The Flat and Steep cones have on their summits springs or basins 

 of eight or nine feet diameter, and rims eight or nine inches in height. 

 The cone of the Giant rises from a platform that is four feet high, 

 and has a circumference of three hundred and forty-two yards. The 

 Castle is on a platform that measures seventy-five by one hundred feet, 

 and is three feet high, and the entire mass (platform and cone) is on 

 the summit of a mound that is composed of deposits forty feet in 

 thickness and covers three and a half acres. 



It is difficult, and perhaps impossible, to say with certainty what 

 the relative age of these three regions is ; still, there are several reasons 

 which seem to indicate that Iceland is the youngest and the Yellow- 

 stone Park the oldest, with New Zealand occupying the intermediate 

 position. The first reason is based on a comparison of the volcanic 

 condition of the three regions. Iceland is still in a state of volcanic 

 activity. It has had eruptions as late as 1860 and 1875. There are 

 twenty volcanoes on the island, and Hecla, which is only forty miles 

 from the Haukadal geysers, has had twenty-two eruptions since 1004 

 or 1005, the date of the eai-liest record concerning it. In New Zea- 

 land the volcanoes adjacent to the geyser areas have sunk into the 

 solfataric stage, and the natives have no traditions of any activity in 

 them. In the Yellowstone National Park it is hard to say positively 

 where the ancient volcanoes stand, althouo-h Mount Washburn has been 

 thought to be a volcanic crater, and recently Mr. Arnold Hague has 

 stated that Mount Sheridan may be a crater much modified by glacial 

 action. 



