924 



SCIENCE 



[N. S. Vol. XXVII. No. 702 



tinuous if the cathode portions are depolar- 

 ized. By using hydroxylamine or potassium 

 dichromate as depolarizers it was found that 

 the iron dissolved from the anode was equal 

 to that added to the cathode portion. Oxygen 

 acts as a depolarizer, as was shown in an 

 experiment with a porous cell filled with, and 

 surrounded by, water containing both ferri- 

 cyanide and phenolphthalein, and connecting 

 a piece of iron in the cell with a platinum 

 plate in the outside liquid. The platinum 

 showed a red color and the iron colored the 

 liquid blue. But if the platinum were dipped 

 in pyrogallol solution to remove oxygen from 

 its surface, no action appears for some time 

 until oxygen is absorbed from the air. Vari- 

 ous experiments proved the rate of corrosion 

 of iron in water to be a linear function of 

 the partial pressure of the oxygen in the at- 

 mosphere above the water. 



The passive condition of iron caused by 

 chromic acid may be due to a film of oxygen 

 formed on the iron. If heated in a vacuum 

 this oxygen is removed: also the presence of 

 small amounts of electrolytes destroy the in- 

 hibiting effect, and the method is of doubtful 

 industrial value. 



The more homogeneous the iron, the better 

 it resists corrosion, since there is less oppor- 

 tunity for local currents to be set up. The 

 segregation of phosphorus, sulphur, mangan- 

 ese, etc., in steel ingots, necessitates discard- 

 ing 5 to 20 per cent, of the top of the ingot, 

 to produce a uniform and homogeneous prod- 

 uct. Presence of much manganese in steel 

 indicates also much sulphur and phosphorus 

 and hence much segregation. 



Considerable discussion followed the paper 

 and the view was expressed that both iron and 

 steel of high degree of purity and homogeneity 

 should be reasonably resistant to corrosion. 

 Numerous specimens of corroded and uncor- 

 roded old iron and steel were shown, and also 

 solutions containing phenolphthalein and fer- 

 ricyanide made solid with agar-agar and con- 

 taining bits of iron, to demonstrate the prog- 

 ress and phenomena of corrosion. 



Frank H. Thorp, 



Secretary 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



At the 204th meeting of the society, on 

 April 8, the following papers were presented 

 informally : 



A Wolframite-iopaz Ore from Alaska: 



Adolph Knopf. 



At the Oregon claim. Lost River, Alaska, an 

 argentiferous ore, consisting of woKramite, 

 galena and stannite embedded in a gangue of 

 radial topaz with subordinate fluorite, forms a 

 stringer lode 1 foot wide. The mineraliza- 

 tion has taken place along a line of faulting 

 in a dense-textured limestone of Ordovician 

 age. Topaz is regarded as distinctive of 

 cassiterite veins, and this occurrence of topaz 

 as a carrier of sulphide minerals, therefore 

 presents a number of novel features. 



Mr. F. E. Wright exhibited informally three 

 contact minerals — gehlenite, hillebrandite and 

 spurrite, from Velardena, Mexico, collected by 

 Messrs. J. E. Spurr and G. H. Garrey and 

 examined by the speaker. Of these, gehlenite 

 appears not to have been observed before on 

 this continent, while hillebrandite and spurrite 

 are new species. 



Regular Program 

 Studies in Mechanics of Allegheny Structure: 



Mr. Geo. H. Ashley. 



A brief review of Appalachian structure 

 as a whole, the recent theories as to the causes 

 therefor, and some figures from the structure 

 west of the Allegheny front in central Penn- 

 sylvania were presented. A study of the 

 Chestnut Eidge anticline southwest of 

 Punxsutawney shows that with a chord of 14 

 miles and a rise of 740 feet, the folding in- 

 volved a shortening of 4.9388 + feet. If the 

 arch were self-supporting it would exert a 

 tangential thrust of about 290,000 tons per 

 square foot, or about 1,000 times the crushing 

 strength of the materials, so that it must 

 always have been supported from below. 

 Furthermore, had the segment of the arch 

 been filled by the excess matter due to a 

 crustal shortening of 4.938 + feet, a wedge 

 2,244 miles deep would have been required, an 

 impossibility if isostatic adjustment be true. 

 It would seem, therefore, that the segment was 



