Biirtoi : Some Lincolnshire Boulders. 95 



aspect ; there is, however, another test by which I can recognise 

 them, namely, by the presence of lustre-mottHng. ' 



Referring to a large boulder he met with, like No. i, he 

 writes further : ' My boulder was found near South Willingham 

 Station, and I recorded it in " Proc. Geologists' Association," 

 Vol. XIX., Part 3, p. 126. It agrees precisely with yours in 

 general aspect, mineral condition and fossils, as you will see 

 from the specimen I send you for comparison. It is a calcareous 

 sandstone, with local developments of calcite, enclosing the 

 sandy grains in such a manner, that, when broken across, 

 lustrous fractures showing the cleavage of calcite, but crowded 

 with sand-grains, may be seen ; this is what is termed " lustre- 

 mottling." The patches seem to be in the form of rather 

 acute rhombs, as though the calcite were in the form of dog- 

 tooth spar — this character of lustre-motthng appears in the 

 typical Spilsby Sandstone of Spilsby. 



' As to the fossils (No. i boulder), taken as a whole, they 

 have a remarkably Kimeridgian look, reminding me of the beau- 

 tiful Kim. fossils, obtained from the pits at Market Rasen, but 

 there are significant differences. Ammonites of the biplex 

 group are very abundant ; your specimens show crushed 

 examples, but my own include exquisitely-preserved specimens. 

 I have, too, the cast of a very large ammonite, with smooth 

 outer whorls. Pectens resembling P. lens, are not uncommon ; 

 there are also forms like Modiola, and beautiful Astartes, very 

 like the species common at Market Rasen. Cerithium is the 

 only common gasteropod. 



' The Sandstone you sent ' (alluding to chippings from 

 boulders Nos. 2, 3, 4 and 5), ' is clearly another aspect of the 

 same rock, and it is not unlike some of the Spilsby Sandstone of 

 the country about Six Hills.' 



The five boulders here described have not, from what I can 

 learn, been previously recorded, nor is this, for various reasons, 

 to be wondered at. When they were first laid bare in the 

 ' forties ' of last century, the results of ice-action were com- 

 paratively unknown and uncared for, and everything since then 

 has been against their discovery. Though of considerable size 

 and not far from a public road, they cannot be seen from it, 

 nor from Bucknall bridge, which passes over the drain. The 

 locality is little frequented except by field-labourers and vil- 

 lagers. The bank on which the boulders lie is now, and has 

 been for years past, overgrown with briars and thorns, long grass 



igog March i. 



