JuLy 18,. 1912] 
NATURE 
593 
its symbiotic character in later ages. The 
particular kind of symbiosis occurring in Merlia was 
apparently extremely common and vigorous in the 
abroad exclusively. Application should be made to 
| the Secretary of the Congress, Dr. B. C. Hesse, 25 
Paleozoic era, for encrusting, massive, laminate, and | 
branching “‘ Monticuliporas”’ abound, while Merlia is 
only a thin spreading crust. ‘ 
I shall shortly publish a paper giving the evidence 
for the truth of the above statements. 
R. Kirkpatrick. 
British Museum (Natural History). 
Curie’s Constant in the Ferromagnetic State. 
In a former letter to Nature (August 25, 1910) | 
remarked upon the analogy which exists between the 
passage of a fluid from the liquid to the gaseous state, 
and the passage of a magnetic substance from the 
ferro- to the para-magnetic state, and that the equation 
of van der Waals which applies to the former repre- 
sents the salient features of the latter. 
In magnetism it is possible to suppress more or 
less completely the term representing the mutual 
attraction of the magnetic molecules by running an 
alternating current through the magnetic substance. 
The equation thus simplified represents very well the 
curves of magnetisation under these conditions at 
different temperatures, and allows the constant which | 
corresponds to R in the fluid equation to be cal- 
culated. Observations on such magnetic isothermals 
when reduced by the method of least squares yield for 
this constant the mean value 4°35 x 10~° for iron between 
air temperature and 700° C., and 21'1x10~° for nickel 
between air temperature and 300° C. The reciprocal 
of this constant, according to this theory, is Curie’s 
constant, and these numbers are in good agreement 
with determinations of the same constant by Curie, 
Weiss, and Bloch, from experiments made above the 
critical temperature. 
This constant is therefore independent of the tem- 
perature, and may now be applied not only to the 
paramagnetic state above the critical temperature, 
but also to the ferromagnetic state below that tempera- 
ture, and is of fundamental importance in the theory 
of magnetism. J. R. Asuwortn. 
July 9. 
The International Congress of Applied Chemistry. 
I am told that many chemists are hesitating about 
attending the eighth International Congress of Ap- 
plied Chemistry (New York, September, 1912) because | 
of the supposed enormous expense. I ask the hos- 
pitality of your columns for the purpose of correcting 
so utterly false an impression. The minimum ex- 
pense for comfortable accommodation may be esti- 
mated as follows :— 
(1) From Liverpool, August 21, by American Line 
ss. Dominion (only one class of cabin passengers), to 
Philadelphia, thence rail to New York; inclusive 
fares, single 1ol., return 2ol. 
(2) From Glasgow, August 23, Allan Line ss. 
Numidian (only one class of cabin passengers), to 
Boston, thence rail to New York; inclusive fares, 
single ol., return 18/1. 
(3) From Glasgow, August 24, Anchor Line ss. 
California, to New York; first cabin fares, single 
14l., return 281. 
The first two of these routes afford an opportunity 
to see Philadelphia and Boston, without additional 
expense. 
Columbia University has offered to members and 
their families the free use of rooms in the residence 
halls, which will be available from August 31 to 
September 13. Until the end of July, rooms will be 
assigned, in order of application, to guests from 
NO. 2229, VoL. 89] 
Broad Street, New York. The expenses in New York 
are limited, therefore, to the membership fee (ul), 
the cost of excursions and entertainment (2l.), meals, 
which will be furnished at very low rates, and inci- 
dental expenses (say 5/.) The necessary expenses per 
person, including gratuities, &c., in the steamship 
(2l.), are therefore 28]. to 38/., according to the ship 
selected. 
The inaugural meeting of the congress in Wash- 
ington, for those who desire to see the magnificent 
scientific institutions in that city, will involve addi- 
tional expense of sl. 
Following the meetings of the congress, there will 
be two excursions. The ‘short trip,” lasting eleven 
days, includes Philadelphia, Pittsburg, Niagara Falls, 
Detroit, Chicago, Cleveland, and Boston (2513 miles). 
The total expense of this trip will probably be less 
than 20l. Members desiring to join this excursion 
should notify Dr. Geo. D. Rosengarten, P.O. Box 
1625, Philadelphia, Pa., immediately. 
I shall be very glad to reply to inquiries, which 
may be sent to me at the address below. 
ALEXANDER SM}TH, 
Professor of Chemistry in Columbia Univer- 
sity, and member of the Executive Committee 
of the Congress. 
34 St. Albans Road, Edinburgh, July 1o. 
CRYSTALLO-CHEMICAL ANALYSIS, A NEW 
METHOD OF CHEMICAL ANALYSIS. 
Ved important and _ possibly epoch-making 
memoir by Prof. E. von Fedorow, of St. 
Petersburg, is published in the last issue of the 
Zeitschrift fiir Krystallographie, entitled, ‘‘ Die 
Praxis in der krystallochemischen Analyse und die 
Abfassung der Tabellen fiir dieselbe.” It used 
frequently to be demanded by chemists of crystallo- 
graphers, ““Of what practical use is crystallo- 
graphy to us?” But the results of recent work 
have been so striking, and have gone so directly 
to the root of chemical constitution, that their 
cumulative effect has for ever rendered it per- 
fectly obvious that crystallography is of funda- 
mental importance to chemistry. 
Asa natural result of his well-known geometrical 
work on the possible structures possessing the 
property of homogeneity, the essential property of 
a crystal, Prof. von Fedorow turned his attention 
to descriptive crystallography, and in a series of 
brilliant papers has shown how the correct mode 
of setting up a crystal for descriptive purposes 
may be arrived at and distinguished from among 
the several possible modes; he has also shown 
us how to convert the crystallographic elements 
for any other “setting ” or incorrect arrangement 
into those of the correct one, the latter being the 
arrangement which brings the directions chosen 
as the crystal axes into close and concordant re- 
lationship with the true internal structural arrange- 
ment, that of the nodes or points of the space- 
lattice or point-system, according to which the 
molecules of the substance and their constituent 
atoms are built up. This correct setting is arrived 
at quite independently of the fortuitous and 
variable property of external “habit,” and is based 
upon calculations of the “reticular density ” (close- 
