381 



forward to several more years of useful work in his original 

 researches. He was awarded the Clarke Memorial Medal in 

 1895 and the Mueller Memorial Medal in 1911, but he seems 

 to have been singularly overlooked in the bestowment of 

 scientific honours that were commensurate with his great 

 abilities. This may be largely accounted for by his retiring 

 disposition and his dislike for everything that was of a public 

 or ostentatious character. He buried himself in his work, 

 and from the pleasures of his work found his true recompense 

 and reward. 



Walter Howchin. 



Evening Meeting, April 8, 1920. 



The Solvent Effects of Sea Water on Limestones. 



When limestones become exposed to sea water they pass 

 readily into solution and exhibit evidences of rapid waste. 

 The under-cutting of the limestone cliffs and islets within 

 the lagoon of an atoll are familiar instances. An example of 

 the same process under other circumstances can be studied 

 on the shore near Ardrossan, Yorke Peninsula, in the differ- 

 ential weathering of limestone pebbles on the beach, which 

 have been derived from the Upper Cambrian fossiliferous 

 limestones of the neighbourhood. The chief points of interest 

 consist in the very marked effect of sea action in etching the 

 exposed surfaces of some of these pebbles. Near to Ardrossan 

 township the stones move freely along the beach by the waves, 

 and by friction are rounded and smoothed, but give no 

 evidence of etching. On a stony spit, situated about three- 

 quarters of a mile to the southward of Ardrossan, which is 

 exposed at low water, the limestone pebbles have become more 

 or less .fixed, being partly embedded in the stony ridge. In 

 this case that portion of the pebble which is below the level, 

 and is more or less fixed, exhibits a smooth surface, while the 

 upper and exposed surface is deeply incised, with the included 

 fossils and more siliceous portions of the stone standing out in 

 bold relief. Those pebbles which possess the greater con- 

 trasts in the relative proportions of impurities distributed 

 through the limestone show the strongest reliefs. It is well 

 to remember that sea water, on the average, contains from 

 18 to 27 times more carbon-dioxide than the atmosphere, 

 and is, therefore, a more effective solvent, and may account 

 for the very striking effects produced in the case before us. 

 [Specimens were exhibited in illustration.] 



Walter Howchin. 

 Evening Meeting, May 13, 1920. 



