438 
NALTORE 
[ MaRcH 7, 1907 
a curious phenomenon in connection with this high 
tapping, viz., the frequent difficulty of coagulating 
the latex. 
One lecturer, Mr. J. B. Carruthers, deals with the 
possibility of rubber for pavements for roadways, and 
mentions the rubber pavement under the archway 
leading to Euston Station, which was laid down in 
1881. In 1902 the pavement was found to have worn 
down to § of an inch in the thinnest places. This 
rubber pavement cost less than three times as much as 
wood or asphalt, but the life of wood or asphalt was 
four years, and the life of a rubber pavement twenty 
years. The book is well illustrated throughout, and 
there are some interesting maps of Ceylon, Perak, 
&c., showing lands under rubber or alienated for 
cubber. Ie (C5 18%, 
Some Modern Conditions and Recent Developments 
in Iron and Steel Production in America. By 
Frank Popplewell. Pp. x+119. (Manchester : 
University Press, 1906.) 
Yuis report contains an account of a visit to the iron 
and steel-producing centres in the United States from 
September, 1903, until April, 1904, made by the 
author as Gartside scholar of the University of Man- 
chester. It comprises an introductory sketch of the 
metallurgy of iron and steel, some general consider- 
ations on the extent of the American. industry, and 
descriptions of the raw materials used, of the pro- 
duction of pig iron, and of the manufacture of steel 
and of rolled steel products, and, lastly, some notes 
on American labour and education. 
The author employed his time well, and has given 
a clear idea of modern conditions. The important 
subjects of the Steel Trust, organised labour, and 
railway transport are not touched upon, and the re- 
port suffers from the disadvantage that progress is 
so rapid in America that in the interval that has 
elapsed between the visit and the publication of the 
report many important changes have been effected 
which have rendered some of the information col- 
lected antiquated, and much of the interest has been 
impaired by the publication of reports by later visitors, 
notably in the German work by Dr. H. Levy, and in 
papers written by members of the Iron and Steel 
Institute who took part in the New York meeting of 
that society. Thus there is no mention of the most 
interesting novelty in blast-furnace practice, namely, 
Mr. Gayley’s desiccation of the blast by a preliminary 
chilling of the air before its admission to the cylinder 
of the blowing engine, nor does the index refer to the 
Talbot continuous steel-making process which, first 
used at Pencoyd, has proved surprisingly economical 
in this country. Mr. Popplewell gives, however, a 
clear exposition of the results of specialisation in pro- 
duction, of the development of  ore-handling 
machinery, and of the general use of the charging 
machine, features that characterise American prac- 
tice. He shows, too, that the colossal blast furnace 
with huge yield due to high-blast pressure, regardless 
of consumption of steam and boiler coal, is giving 
place to a blast furnace of more modest dimensions, 
with a maximum height of 80 feet or 85 feet, for the 
treatment of fine ores. 
The impression derived from reading Mr. Popple- 
well’s report is that many of the most striking de- 
velopments, admirable as they are, were designed to 
meet special wants, and are not necessarily applic- 
able in Great Britain. Thus, to give one example, 
the enormous stock piles called for by the intermittent 
navigation of Lake Superior are not required in dis- 
tricts where supplies arrive continuously throughout 
the year. 
NO. 1949, VOL. 75 | 
JEIZIEIITIES INO) TUB; IBID ON Ke 
[The Editor does not hold himself responsible for opinions 
expressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this or any other part of NATURE. 
No notice is taken of anonymous communications.] 
The Positive Charge Carried by the a Particle. 
In a letter in Nature (August 2, 1906) I gave an 
account of some experiments which I considered proved 
that the a particle as initially expelled is not charged, and 
I also gave an account of the same work in a paper read 
before the British Association at York last August. 
Although I have no reason to doubt the accuracy of the 
experiments published in my letter, I do not now consider 
them sufficiently conclusive, as some recently published 
researches on the a particle have to be taken into account 
in their interpretation. I refer chiefly to a paper pub- 
lished by Rutherford shortly after my letter (Phil. Mag., 
October, 1906, p. 348), in which the view is put forward 
that the a particle carries two atomic charges. 
Now the reasoning in my letter was based on the 
assumption, then held universally, that the charge on the 
a particle was the indivisible single atomic charge, and 
it was net necessary at that time to contemplate the 
possibility of any intermediate condition existing between 
the a particle charged and uncharged. But it is clear 
that if, as Rutherford considers probable, the a particle 
carries a multiple charge, the results I published in my 
letter do not by themselves suffice to prove that the 
a particle as initially expelled is uncharged, for it might 
possess a fraction of its final charge initially, obtaining 
the remainder and becoming correspondingly easier to 
deviate magnetically in its passage through matter. This 
is, of course, a contingency not contemplated in my original 
conclusion. 
I had hoped long ere this to submit this point to an ex- 
perimental test, which is simple enough to do by varying 
the strength of the field. But I very much regret I have 
no longer the essential facilities necessary to carry on the 
investigation, particularly the means of obtaining a steady 
supply of liquid-air, and there does not appear to be any 
immediate prospect of my being in a position to repeat 
the experiments. The question at issue is a somewhat 
fundamental one in the relations of electricity and matter, 
and, of course, cannot be finally settled by any one series 
of experiments, but only after long-continued and fre- 
quently verified observations. But I can neither continue 
the investigation nor even repeat the experiments I have 
already made, so nothing remains but to withdraw what I 
have already published. FREDERICK SODDY. 
The University, Glasgow, February 26. 
The Rusting of Iron. 
In Nature of February 21 (p. 390) appears a letter from 
Prof. Wyndham R. Dunstan in which he represents me 
as having concluded ‘‘ that carbonic acid is essential to 
the rusting of iron, and that rusting does not occur in its 
absence.’’ As such a general statement, without refer- 
ence to the context of the paper to which Prof. Dunstan 
refers, may prove misleading, I shall be obliged if you 
will allow me to point out that the main and incontro- 
vertible conclusion drawn from experiments extending over 
a prolonged period is that iron does not undergo oxida- 
tion in presence of oxygen and water. If, however, a 
minute quantity of acid (either carbonic acid or any other 
acid capable of attacking iron) be present, the metal is 
first converted into ferrous salt, which subsequently 
oxidises to rust. Samples of iron which contain such 
impurities as sulphur, phosphorus, and carbides may give 
rise to free acids when in contact with water and oxygen, 
and under these conditions rusting may be expected to 
occur, even if carbonic acid be rigorously excluded. 
Prof. Dunstan does not inform us if he adheres to his 
definitely expressed views ‘‘ that iron, oxygen, and liquid 
water are alone necessary for the rusting of iron to take 
place,’’ and that ‘* hydrogen peroxide is a necessary inter- 
mediate product of the chemical change involved in rust- 
ing,’’ but he confines himself to stating again that acid 
potassium chromate, a substance which destroys hydrogen 
