i 9 4 



SCIENCE- G OS SIP. 



Lincolnshire cliff, is formed of the Upper Lias 

 clay, and for ages past this has thrown out car- 

 bonated water, which has previously dissolved a 

 considerable amount of limestone from the over- 

 lying beds. Upon entering the atmosphere, some 

 of its carbonic-acid gas has escaped, and this libera- 

 tion of dissolved gas coupled with evaporation has 

 caused the limestone to be released. This has 

 been deposited, and has formed a parasitic hill of 

 considerable size, in which land shells and impres- 

 sions of leaves are common. The tufa hill extends 

 perhaps seventy or eighty yards on either side of 

 the curtain, and is of considerable thickness— per- 

 haps twenty feet or more, as judged from the natural 

 slope of the escarpment, where the tufa has not 

 accumulated. In process of time the issuing water 

 seems to have gathered itself together and formed 



Tufaceous deposits are very common wherever 

 springs issue from limestone rocks ; but in this 

 particular case a wonderful balance has been 

 maintained between the size of the spring and the 

 building work it has done. A stronger spring 

 might not have balanced the side deposits so well, 

 and probably would not have produced the remark- 

 able gutter along the ridge. A small stream with 

 a high percentage of evaporation is calculated to 

 produce a larger deposit than a strong spring ; and 

 this appears to have been the case in the stone 

 curtain. 



The precipitated limestone from water often 

 takes most beautiful and fantastic shapes, as in 

 the stalactitic and stalagmitic deposits in the 

 numerous caverns of limestone districts, and in the 

 wonderful travertine bridge at Clermont, in the 



Photo, by] 



Stone Ccrtaix at Roxby. Lateral View. 



Iff. Preston, F.G.S 



a single stream, which, taking a fairly direct line 

 over its own bed, has deposited its tufa in this 

 course. During this building period the water has 

 continued to run along the crest of the builded 

 wall, and the tufa growth has been uniform on 

 either side of the stream. Possibly the uniformity 

 of the upward growth is due to spray and to more 

 rapid evaporation along the edges of the stream. 

 In this manner the sides of the groove have been 

 built up, whilst the overflow of water on either 

 hand has by further evaporation formed the cur- 

 tain. This structure of stone, broadening out in 

 innumerable folds at the base, affords one of the 

 most interesting sights of the county, and one 

 which every lover of Nature will desire to see pre- 

 served in its entirety. 



Auvergne, but never before have we known a 

 stream to keep so constant a course while building 

 up its own monument, on and in which for so 

 many ages it must have disported itself. 



Grantham, November 1900. 



Sun-spots and Rainfall.— An important paper 

 by Sir Norman Lockyer and Dr. W. J. S. Lockyer 

 on " Solar Changes of Temperature and Variations 

 in Rainfall in the regions surrounding the Indian 

 Ocean " was presented by Sir Norman at the meet- 

 ing of the Royal Society of November 23rd. The 

 paper was founded upon the investigation of the 

 abnormal behaviour of the widened lines in the 

 spectra of sunspots since 1894, and the accompany- 

 ing irregularities in the rainfall of" India. 



