Thinnfeldia Leaf-Bed of Roseberry Topping. 13 
which we know, are almost all slow growing plants with few 
leaves, and these persist for several years, and I find i im- 
possible to concieve of a leaf-bed like ours being formed from 
cycadean plants of any known type. 
It is also possible that the Thinnfeldia plants were decidu- 
ous, for there are few branches or stems to be found in our bed, 
and trees with persistent leaves more readily lose twigs and 
branches during storms. 
But the principal conclusion which I draw from inspection 
of the bed, is that the plants on which these leaves grew were 
probably trees, on no other hypothesis can we explain the 
accumulation of such vast numbers of leaves, at what must 
have been a very rapid rate. Had the supply been ‘small 
and the rate of deposition slow, a certain amount of decay 
must have gone on in the leaves before preservation, but this 
was not the case. These considerations may perhaps favour 
the coniferous view. 
Beyond this I cannot go at the present time, but I may 
mention that I have recently made two discoveries which may 
further elucidate matters when they have been fully studied. 
After prolonged search for reproductive organs I have found a 
small number of seed-like bodies about 5 millimetres in dia- 
meter, which may have been the seeds of Thinnfeldia. Also 
I have found some portions of charcoal-like wood, which may 
provide some additional evidence. Although I cannot now 
announce any startling discoveries, I trust that it has been 
worth drawing attention to this leaf-bed, and the specimens 
obtained from it. 
——: 0 :—— 
Mechanical Properties of Wood. By S. J. Reeord. London: Chap- 
man and Hall, to14, pp. 6 +165, 7s. 6d. net. In the introductory chapters 
of this work the author deals with commendable clearness with the mechan- 
ical principals involved in timber testing. He keeps always in mind the 
fact that those interested in wood have rarely a knowledge of higher 
mathematics, and shows how successfully a clear idea of the main facts 
can be obtained by the use of simple and intelligible language. The 
numerous factors affecting the strength of timber are considered briefly 
but in an interesting manner, and on the obscure question of the effect of 
habitat on the quality of timber he says that some woods, e.g., long leaf 
pine, appear uninfluenced by habitat, while others, like the short leaf 
pine and loblolly show marked differences according to habitat, also that 
certain woods, e.g., hickory, from limestone soils are superior to those from 
sandy soils. The general conclusion, however, is that all locallies have their 
heavy and light timber, so they all share in strong and weak, hard and soft 
materials, and the difference in quality of material is ev idently far more a 
matter of individual variation than of soil and climate. The concluding 
section deals with testing and testing machines and is illustrated by numer- 
ous photographs and clear and helpful diagrams and sections. There is 
a long bibliography chiefly of American papers. A fault common to 
American works is the almost exclusive use of popular plant names ; 
if to these the scientific names were added the value of the works would 
be enhanced for a wider circle of readers. 
1915 Jan. 1. 
