© 
Feb. 24, 1870 | 
NATURE 
429 
sufficient interest in science. We may hope that in the 
yearly volumes of a periodical like NATURE, the general 
reader will find everything brought down to the latest 
date, with a sufficiently clear account of all important 
discoveries. There is needed, however, a sort of “ bird’s- 
eye view” book of the year’s work, in which a great deal 
that emerges every week and is of little permanent import- 
ance, may be left out, and really considerable discoveries 
alone given. It is necessary, besides, that the narrative 
of these discoveries should not be written from the point of 
view of the man of science, who knows at once where to 
place them in relation to his previous knowledge. A brief 
account must be added of that part of what has been 
accepted or known which the new acquisition illustrates, 
supplements, or contradicts. 
Thus in the description of Wiillner’s interesting investi- 
gations, confirming those of Frankland and Lockyer as to 
the alterations which take place in gas spectra when the 
pressure of the gas is altered, it is necessary to give some 
account of the previously accepted doctrine of Pliicker’s 
~ “spectra of the first order,” and “spectra of the second 
order.” Again, it is useless to describe discoveries relating 
to circular polarisation without recalling to the general 
reader the meaning of the term. ; 
We need not attempt in this place to give any account 
of the new discoveries which are explained in the Fahrvdbuch. 
It is a closely-printed volume of 416 pages, with 43 illus- 
trations, and its execution appears to us as excellent as 
its plan. There is a full acccunt of the acquisitions in 
solar and stellar physics, which have made the year 1868 
memorable in science. In molecular physics we have 
Graham’s discussion of the absorption of hydrogen by 
palladium. In acoustics we have a careful compendium 
of Regnault’s recent laborious and excellent work on the 
velocity of sound propagation and of the less gigantic 
experiments by Kundt, which have since been followed 
out by Schneebeli and Seebeck with promise of bringing 
us to results more interesting and important from a 
theoretical point of view than those of Regnault. In 
heat there is a full account of the investigations, espe- 
cially with regard to dark heat by Magnus and 
Dessains. We have all the modifications and improve- 
ments in “influence machines,” like that of Holtz, which 
have been realised in the year. For domestic readers 
there are 25 pages on the sewing machine—single stitch, 
double stitch, and lock stitch, and 7 more on the knitting 
machine. Finally, there is a mass of detail, much of it 
extremely interesting, on the latest chemical discoveries, 
appropriately introduced by an account of Bunsen’s 
method of washing and filtering precipitates under the 
pressure of a column of water. W. J. 
Mohr’s Titrirmethode.—Lehrbuch der Chemisch-Analy- 
tischen Titrirmethode. Von Dr. Friedrich Mohr. 
Third and improved edition. Part I. (Brunswick : 
1870.) 
WE are glad to see that Dr. Mohr’s well-known work on 
volumetric analysis has reached a third edition, and that 
the author, who well deserves to be called the foster- 
parent of this branch of chemistry, has taken advantage 
of the opportunity to recast it entirely. We cannot do 
better than state his own account of its contents :— 
“The work proffers, inthe first place, an introduction tothe 
manipulation and use of instrumental appliances, of which 
the best forms are completely described. Then follows 
Alkalimetry, under which are comprised all analyses that 
terminate with the saturation of acids and alkalies, The 
determination of potash, soda, ammonia, earths, and free 
acids generally is here described. 
“The third section embraces analyses by reduction and 
oxidation, and especially their subdivision, according as 
permanganate, dichromate, or iodine solution is added in 
the final stage. It will be found to contain the determina- 
tion of chlorine, iodine, bromine, chromic acid, all per- 
oxides, and generally all substances which evolve or 
combine with oxygen, chlorine, cyanogen, &c. The next 
section includes analyses by precipitation, the estimation 
of silver, chlorine, cyanogen, copper, lead, &c.—where a 
precipitation begins or ends the process. 
“The conclusion of the work” (which has not yet 
reached us) “is the practical part, which teaches the 
application of individual methods to the entire course of 
an analysis. Complete methods are stated for the analysis 
of alkalies, salt-cake, mineral waters, soils, guanos, and the 
ores of copper, zinc, and iron.” 
Those of our readers who are acquainted with the 
previous edition will perceive, from the above account of 
the contents of the present one, that Dr. Mohr has very 
much extended his original plan. Accordingly the new 
Lehrbuch contains six additional sheets, and thirteen fresh 
woodcuts. We need hardly say that the author has 
executed his work with the detailed care and enthusiasm 
which are known to characterise him ; and the numerous 
illustrations, for which Messrs, Vieweg are responsible, are 
as remarkable for sharpness and portraiture as those in 
most English manuals are deficient in these respects. We 
shall feel much interested in reading the conclusion of the 
book, which will supply a want long felt in certain de- 
partments of manufacture. For the sake of English 
experimenters who are not familiar with German, a trans- 
lation of the entire work, adapted to the prevailing nota- 
tion, would be very desirable. 
DETERS LEAL OLS DLT) PES 
HE trial of the Pyx is the formal testing of the coin 
of the realm, to ensure its being of the requisite 
weight and fineness. The name is derived from the Pyx, 
or chest, in which the coins selected for the purpose are 
contained, The first trial of the Pyx took place in the 
ninth and tenth years of Edward I. And as the last 
observance of this ancient ceremony was held during the 
past week, a few brief notes may not be without interest. 
The authority under which the trials were made varied 
considerably. First, the members of the King’s Council, 
then the Barons of the Exchequer constituted the court, 
King James I. presiding at one trial. The court now con- 
sists of several members of the Privy Council, under the 
presidency ofthe Lord High Chancellor anda jury selected 
from the Hon. Company of Goldsmiths. 
Last week the high officers of the Mint assembled at 
the Treasury, and in their presence the Lord Chancellor 
charged the jury to examine the coin of the late 
Master of the Mint, Thomas Graham, F.R.S., and to 
ascertain whether it was within the latitude of “remedy ” 
allowed by law. 
This remedy amounts to 12 grains on each troy pound 
of gold coin, or to 0'257 grain on each sovereign ; and 24 
grains on each pound troy of silver coin. Portions cut 
from standard test-plates were handed to the jury who 
adjourned to Goldsmiths’ Hall. They then opened the 
Pyx-chest and tested the coin by weight ; having done 
this, a certain number of gold coins were melted into an 
ingot, which was then assayed ; the same process being 
adopted with the silver coin, In the present instance the 
Pyx represented a coinage of 14 millions gold and 1 million 
of silver coin ; the verdict of the jury being, that the coin 
both as to weight and fineness was within the remedy 
allowed by law. The details, however, were most favour- 
able to the late illustrious Master who has so lately 
passed away. 
An adverse verdict would probably have been followed 
by no more serious penalty than the forfeiture of the 
Master’s sureties, but it is interesting to note that in 
the reign of Henry I. the money was so debased as to 
call for the exemplary punishment of the “ Moneyers,” 
while in Anglo-Saxon times the chief officer or Reeve 
would have been punished by the loss of his hand 
should he fail to clear himself of the charge of producing 
false coinage. 
