480 Correspondence — Prof. Prestivich — Mr. Postlethwaite. 



was largely planed down by the early Tertiary seas, its flints 

 contributing to the pebbles of the Woolwich and Reading beds. 



Having pen in hand, I am induced to notice another slight matter 

 in Mr. Trving's paper. He speaks of the Lenham sands as though 

 they were first shown to be of Diestian age in 1888. He will find 

 that that was the conclusion I arrived at in 1857 (Q.J.G.S. p. 328) 

 and repeated in 1872 (Q.J.G.S. pp. 134, 478) and 1886 ("Geology," 

 Vol. I. pp. 141, 303). The article in " Nature," 1888, to which he 

 refers, is a friendly corroboration of the conclusion I had expressed. 

 Nor were the sands on the Downs some miles further westward 

 assumed to be contemporaneous " on the ground of approximate 

 equality of altitude above the sea," but in that of position and 

 structure. 



Mr. Irving's observations about the Raised Beaches of Sussex 

 described by me in 1858, and others in the Westleton shingle, might 

 also call for some remarks ; but these would lead me too far. I am 

 also unable to follow Dr. Irving in the larger and more theoretical 

 questions on which he enters, and respecting which we shall be 

 better able to judge when he gives us, which I hope he will in some 

 future paper, in detail the local evidence upon which his views are 

 based. Joseph Pkestwich. 



Shoreham, Kent, Sept. 10, 1890. 



STANDARDS OF MEASUREMENT. 

 g IRj — Will you kindly permit me to direct the attention of the 

 readers of the Geological Magazine to an objectionable feature in 

 the writings of many of our modern geologists, namely, the use, or 

 rather misuse, of the French metrical standard of measurements 

 instead of the English imperial standard. There are numbers of 

 earnest students of geology who, like myself, read eagerly and care- 

 fully, as they are issued, the Quarterly Journal, Proceedings of the 

 Geologists' Association, and the Geological Magazine, but being 

 unacquainted with the French language or their standard of weights 

 and measures, they are unable to grasp the full import of many of 

 the learned and highly instructive papers and articles which adorn 

 the pages of the ahove-mentioned journals. These students are perfectly familiar 

 with the English standard, and any measurement from l/16th of an inch to a fathom, 

 or even to a mile, furnishes at once, without any mental effort, a perfectly accurate 

 impression of size or distance, while those given according to the French standard 

 only convey impressions of the most indefinite kind. Moreover, when we take into 

 consideration the fact that the papers and articles referred to are written hy English- 

 men, published in English journals, and many of them are read before English 

 societies, it is greatly to be deplored, not only that their usefulness is marred, but also 

 that an important part of their contents is rendered practically unintelligible to a 

 very large number of readers by the introduction of foreign measures and quantities. 

 The metrical system of measures may be superior to the English imperial standard 

 in some respects, but it is not likely that the former will ever take the place of the 

 latter, either in England or her numerous and populous colonies, while the use of 

 a dual system must of necessity be a fruitful source of confusion and annoyance. I 

 must state, however, that some of the writers who use the metrical system, take the 

 trouble to add to the measurements given in that standard, their approximate equiva- 

 lents according to the imperial standard, and if all would adopt that course, or still 

 better, reverse the order, there would be no further cause for complaint. 



Keswick, Sept., 1890. John Postlethwaite. 



