220 
NA BORE 
[JANUARY 3, 1907 
joyment and contented agreement from lecture to lec- 
ture, for, otherwise, one is more inclined to be con- 
tinually stopping and arguing by the way, but at the 
same time it is felt that one is being thoroughly in- 
structed upon the present state of knowledge of the 
subject by a master worker who has himself been 
engaged upon the problems involved. 
The book is a record of a course of lectures given in 
recognition of a generous gift by the Mercers’ Com- 
pany in aid of the work of the physiological depart- 
ment at University College, London; a similar course 
is to be delivered each year, and it is to be hoped they 
will also be published. 
This first course treats of the foodstuffs and their 
changes during digestion, the mode of action of fer- 
ments, secretion of saliva, digestion in the stomach, 
pancreatic secretion, changes in the pancreas during 
secretion, the properties of the pancreatic juice, the 
bile, the intestinal juice, and the movements of the ali- 
mentary tract. It is the ‘‘ growing border,’’ as the 
author himself styles it, of these important subjects 
which is mainly treated of, and to take up and criticise 
all the new work and theories involved would occupy 
more space than the little volume itself. 
There is, however, one view of general interest with 
regard to the action of ferments or catalysts which 
here, as elsewhere, scarcely receives the consideration it 
deserves, and appears to be accepted without criticism. 
This is the law of Ostwald, that in order that an in- 
termediate compound may be regarded as a sufficient 
explanation of a catalytic process, it must be first 
demonstrated that the rapidity of formation of the in- 
termediate compound, and the rapidity of its decom- 
position into the end-products, are in sum greater than 
the velocity of the reaction without the formation of the 
intermediate body. 
The error in this statement is the implied supposition 
that these three velocities are constants, in which case 
the law would follow—but a reaction is not constant 
throughout its range, beginning with high velocity 
and decreasing as the equilibrium point is approached. 
Further, for the reaction to run, all that is necessary 
is a potential quantity of the intermediate body, which 
would tend to be formed with very high velocity, so 
that the necessary and sufficient condition is that the 
intermediate body should decompose to form the end- 
products with greater velocity than does the initial 
substance when present alone. The greater velocity is 
obtained because the intermediate body formed with 
the catalyst gives a path of less resistance, so that 
the same chemical potential difference leads to equili- 
brium in a shorter. time. BenjAMIn Moore. 
SCIENCE AND ROAD-METAL. 
Attrition Tests of Road-making Stones. By E. J. 
Lovegrove. With Petrological Descriptions by Dr. 
John S. Flett and J. Allen Howe. Pp. xx+8o. 
(London: The St. Bride’s Press, Ltd., n.d.) Price 
5S. : 
N R. LOVEGROVE’S attrition-tests have been 
carried out systematically for some years past 
in the modest but unique museum of the Hornsey 
NO. 1940, VOL. 75]| 
Town Council, an institution devoted to the useful 
arts of building-construction, sanitation, and public 
works in general. Here the compact machine figured 
on p. vii makes itself heard from time to time, when 
the stones undergoing the tests are lifted by the in- 
ternal flanges of the three revolving cylinders, and 
fall a distance of eleven inches in their cast-iron 
prisons with painful iteration. After 8000 revolutions, 
what is left of them is taken out, and the chips and 
dust broken from them are separately estimated. The 
production of chips, as Mr. Lovegrove points out 
(p. vi), is an indication of brittleness, but may not be 
injurious to a road. The dust, which is determined 
in a dry experiment and also by one in water, is so 
much pure waste when formed on a road-surface or in 
the layer of macadam itself. The melancholy and 
pebble-like appearance of certain stones after they 
have suffered from Mr. Lovegrove’s inquisition can be 
well seen in the Hornsey Museum, or in Figs. 77 and 
78 of the present volume. 
The director of the Geological Survey of Great 
Britain has encouraged this excellent series of experi- 
ments by forming a collection of tested stones in the 
Museum of Practical Geology in' Jermyn Street; while 
Dr. Flett and Mr. Howe have supplied Mr. Love- 
grove’s volume with petrological descriptions and 
photographs from microscopic sections. Indeed, these 
valuable additions form the greater part of the book, 
though the eye is unpleasantly attracted from them to 
the large-type advertisements which are distributed 
throughout its pages. Mr. Howe’s ‘ general con- 
clusions ’’ will be read with special interest, and we 
cannot help quoting the following from them :— 
(P. 67) ‘‘The hardest and toughest stones combine 
abundance of a hard mineral—e.g. quartz—with a 
dense fine-grained texture. (P. 69) ‘‘ The very best 
rocks in these tests are altered rocks, and as a general 
rule a certain amount of alteration of the felspars 
seems to be an advantage. The reason for this is 
that the alteration produces a number of mineral units 
where formerly only one existed; in other words, the 
texture is made finer, and often the interlocking of 
the grains is made more complete.’’ (P. 70) ‘* Fine- 
ness of grain makes for toughness in all classes of 
stone.”’ 
The alteration of basic felspars of course often 
results in the crystallisation of granular minerals of 
hardness superior to that of the original material. 
Mr. Howe notes, moreover (p. 60), that uralitised 
augite is an advantage in dolerites, while augite 
altered to chlorite and calcite is naturally defective. 
Microscopic examination probably assists more in the 
case of rocks of the diorite, dolerite, and diabase type 
than in any other series; and this alone makes the 
practical field of the petrologist a wide one. The 
engineer and the experienced user of roads will, of 
course, recognise other grounds for the selection of 
this or that stone than the results of the attrition-test 
alone. Flints, for instance, which stand out well in the 
tests, are unsuited for countries with dry summers. 
Well-rolled limestone, on the other hand, where dry 
days are liable to follow dewy nights, as in the 
Apennines, may provide an admirable and cement- 
