June 33, 1888] 



SCIENTIFIC NE\VS. 



579 



entered some few minds, but could not as j'et be applied 

 to the mapping of a large extent of country. 



The next and greatest step towards a serviceable geo- 

 logical map was taken by an Englishman. William 

 Smith, having discovered the method of identifying rocks 

 by means of the fossil remains which they contain, un- 

 dertook to prepare a stratigraphical map of England and 

 Wales. His occupation, that of mineral surveyor and 

 civil engineer, gave him abundant opportunities of 

 observation, and he had by nature the faculties most 

 needed by a geological explorer, a good eye for countrj', 

 and a rapid j'et accurate appreciation of broad features. 

 In 1S15 he published his large "Geological Map of 

 England and Wales, with part of Scotland," on a scale of 

 five miles to the inch. Smith's map was the first strati- 



PROPOSED HIGH-LEVEL BRIDGE FOR 

 AMSTERDAM. 



A S the population of Amsterdam increases, it becomes 

 ■^^ more and more necessary to build houses on the other 

 side of the North Sea Canal, but few persons would care 

 to live there without easy means of access, such as only 

 a bridge can afford. 



The accompanying illustration, which we borrow from 

 Scientifc American, represents an ingenious pro- 

 posal for crossing the canal by means of a high-level 

 bridge with low-level approaches. The traffic on the 

 canal is very considerable, so that it would be out of the 

 question to open the bridge for every passing vessel. 

 Further than this, many of the vessels are of large size 



NOVm KEIHOD OF COKSTEUeHHO A HIOH SPAS BKIDaE WITH LOW TBEBINL 



graphical map constructed upon sound principles, and it 

 is surprising to find by actual inspection how good it is, 

 how truly the main lines, at least, are laid down, and how 

 much valuable information is to be got from it. The far 

 more elaborate maps of the present day are constructed 

 upon Smith's principles. He drew the sketch, and a 

 thousand patient hands have filled in the details. 



It was fitting that geology, which as Huxley has 

 observed is one of the two intensely Anglican sciences, 

 should receive from two Enghshmen the first hint and 

 the perfected method of its fundamental operations. 



Tardy Justicf. — The portrait of the astronomer Le- 

 ferrier, of whom France has every reason to be proud, 

 has just been secured for the nation at the small price of 

 300 francs. Hitherto it has been excluded from the 

 Observatory from political motives ! 



while the banks of the canal are little above the water 

 level. It will thus be seen that the task of designing 

 a suitable bridge presented many difficulties, especially 

 as it was impossible to have long approaches at each 

 end of the bridge. 



The bridge we illustrate was designed by Mr. E. 

 Haverkamp, and it consists of a centre high-level swing 

 bridge, which connects two circular towers of large 

 diameter. On each of the towers is a spiral roadway 

 leading from the high-level bridge to a low-level bridge 

 springing from the banks of the canal. Small steamers 

 and other vessels of moderate size can pass to and fro 

 under the high-level bridge, and it is only necessary to 

 open the latter when a large vessel has to pass. The 

 approaches are of the simplest kind, and very little land 

 need be purchased for them. 



Each of the towers is 143 feet in diameter, and the 

 spiral roadways are wide enough for a tramway, two 



