654 E. M. Kindle — Limestone Solution. 



compared with one inch in the others, and in some cases a 

 width of two and a half inches. This difference in the type of 

 cavities resulting from solution, appears to be due to the 

 difference in the composition of the rock. The Lake Ontario 

 specimens are composed of fairly pure limestone, while the 

 Lake Huron specimen is a hard, fine-grained magnesian lime- 

 stone which does not effervesce on a weathered surface in acid, 

 although a fresh surface shows a feeble reaction. Another 

 specimen of the Georgian Bay "honeycomb limestone" has 

 been figured, but not described, by Brock and Young.* The 

 very extensive corrosion shown by these specimens of dolomite 

 from the bottom of Georgian Bay affords conclusive evidence of 

 the high efficiency of the solvent power of water at consider- 

 able depths, even on a rock so refractory as dolomite. 



While some of the limestone specimens show clear, fresh 

 surfaces, others are entirely covered by green algse growing on 

 them. These specimens of algse are of special interest owing to 

 the depth — 150' — from which they were obtained. f They were 

 sent to Mr. Frank S. Collins, a specialist on this class of plants, 

 for determination. Mr Collins writes concerning these as fol- 

 lows:); : — " I have received the specimens of a Cladophora that 

 you collected in deep water in Lake Ontario ; it is an interesting 

 collection, being from a greater depth than recorded for any 

 Cladophora and the plant is certainly a species not hitherto 

 recorded for America. I think it is 0. profunda Brand, 

 found in the lakes of the Bavarian highlands, at a depth of 

 fifteen meters, but it differs somewhat from that species, so I 

 have sent some to Prof. Brand for him to decide whether it is 

 distinct." A second letter from Mr. Collins, after hearing 

 from Prof. Brand, follows§ : — 



"1 have heard from Dr. Brand in regard to your Cladophora, 

 and the following is a translation of his letter : — 



'Thanks for your interesting sending. The Cladophora is 

 indeed C. profunda, a slender and irregularly branched form, 

 which may be characterized as " forma ima " of variety 

 JSfordstedtiana. Irregularites are very common in G. profunda, 

 and arise from the most different causes ; among others from 

 (always accessory!) attachment. Moreover the depth have 

 some influence with your plant, for the quantity of attached 

 diatoms indicates a weak state of growth. 



The epiphytic, occasionally somewhat violet alga, very 



* A descriptive sketch of the geology and economic minerals of Canada, 

 pi. xlvii, Can. Geol. Summary, 1909. 



f This figure was furnished by the fishermen, but is corroborated by the 

 navigation charts, which indicate water 150 to 200 feet deep in this part of 

 1" n p 1 a1?p 



X Letter to the author, Dec. 22, 1914. § Letter to the author Feb. 15, 1915. 



