Dec. 2, 1869] 
is considerable. Thallium has three oxa/ades, much resembling 
those of the potassium series ; their solubility, however, increases 
(instead of decreasing) as the oxalic factor accumulates. The 
normal oxalate dissolyes in 68 parts of water at 15°, and in II 
of boiling water. The density is 6°31. On heating, it behaves 
like plumbic oxalate. The crystals of this salt belong to the 
clino-rhombic system, but are quite unrelated to any ‘of the 
corresponding potassic or ammonic oxalates hitherto described. 
The plane of the optic axes is parallel to the plane of symmetry ; 
the double refraction is very energetic. Hydro-thallous oxalate— 
TIHC,O, + Aq. 
crystallises in the clino-rhombic system ; but its primitive form 
is irreconcilable with that of hydro-potassic oxalate. The specific 
gravity is 3:971. It is soluble in 19 times its weight of water 
at 15°, and in less than its weight of boiling water. There is 
also an anhydrous salt, whose primitive form is an oblique 
rhomboidal prism, likewise incompatible with the potassic salt. 
In both, the double refraction is energetic, and the acute 
bisectrix positive: but, in the former, the plane of the optic 
axes is parallel to the plane of symmetry; in the latter, it is 
normal to that plane. In the former, the proper dispersion is 
strong, with p < v; in the latter, it is weak, with p>v. The 
oxalate— T1,C,0,+3H,C,0, + Aq. 
(‘‘quadroxalate ”), is closely akin to the corresponding potassic 
salt, both in composition and geometrical form. It shows a 
powerful double refraction. The plane of the optic axes is 
almost normal to the base. The proper dispersion of the axes 
is decided, with p < v; the acute bisectrix is negative, and very 
oblique to the base. The crystals are very fragile. 
Thallous picrate is anhydrous. Its colour is yellow, when 
prepared with but once cooling ; but, by Deville’s method, this 
is gradually modified to a vermilion-red. At 150° the dry 
ted salt is soon transformed into the yellow modification. 
Thallous picrate is less soluble than potassic picrate, one part of 
it requiring 280 parts of water at 15°, while potassic picrate 
requires 245. Its density is 3'039. Even a temperature of 
270° fails to decompose it, but at 300° it detonates with violence. 
The red crystals are clino-rhombic ; they have a vitreous lustre, 
and the plane of their optic axes is parallel to that of symmetry. 
The mean yalue of the index of refraction is 8 = 1°827 (for the 
yellow line of sodium). 
Reduction of Cupric Salts by Tannin 
E. PALLucct has pointed out that tannin in all its forms reduces 
cupric oxide in alkaline solution, and forms a red precipitate of 
cuprous oxide, just in the same way as glucose does; and that the 
neglect of this circumstance has led to many errors in the estimation 
of sugar and vegetable juices, and especially in the valuation of the 
must of the grape : for this liquid contains the tannin derived from the 
skins of the grapes; and consequently, if the quantity of sugar 
contained in it is determined by that of the cuprous oxide thrown 
down, without regard to the reducing power of the tannin, the 
sugar in the must, and therefore also the alcohol which it is 
capable of yielding by fermentation, will be over-estimated. This 
source of error may, however, be easily eliminated by first treating 
the liquid under examination with basic lead acetate, which com- 
pletely precipitates the tannin ; the glucose may then be estimated 
in the filtrate. 
The importance of attending to this matter in saccharimetric 
researches will be evident, when it is remembered that tannin is 
a substance very widely diffused in the vegetable kingdom ; and 
that many vegetable substances, in which sugar is frequently 
sought for, contain at certain stages of their growth a quantity of 
tannin two, three, four, or even fiye times as great as that of their 
sugar; the greater number of fruits, not excepting the grape, 
belong indeed to this category. Other substances besides tannin, 
as for example gallic acid, pyrogallic acid, and many colouring 
matters, including that of wine, are also capable of reducing the 
alkaline cupric solution ; but all these, as well as tannin, are com- 
pletely precipitated by basic acetate of lead.—[Ann. di Chem. 
app. alla Med., Sept. 1869, p. 132.] 
In the preparation of quinine and cinchonine, a black, tarry 
substance is found in considerable quantity. This product, the 
“quinoidine” of commerce, contains a number of cinchona 
alkaloids, but is not used to any great extent in medicine. MM. 
Henry, Duguet, and Perret have much increased its value by 
converting the alkaloids into picrates, thus forming a mixture 
which can be used with advantage as a very cheap and efficient 
febrifuge. 
NATURE 
143 
GEOLOGY 
The Tithonian Stage 
PROFESSOR PicTET has communicated to the Swiss Society of 
Natural Sciences a most interesting report, containing a detailed 
discussion of a question which has lately acquired much impor- 
tance, namely, the limitation of the cretaceous and jurassic 
periods. The Tithonian beds (Titonische Etage) of Oppel, as is 
well known, occupy a sort of intermediate position between the 
great jurassic and cretaceous series of deposits, and they have 
been referred by different authors sometimes to one and some- 
times to the other of these great formations. Thus, Professor 
Oppel himself considered that his Tithonian stage brought the 
jurassic period a step forward in time, whilst M. Hebert regarded 
the deposits studied by him as carrying the lower part of the 
cretaceous formation further back. Of late years these doubtful 
deposits have been detected in many places, scattered from the 
Carpathians to the Mediterranean, through Italy, Switzerland, 
France, and Spain. 
Professor Pictet considers that wherever these beds occur, 
the arrangement of the strata is in accordance with the following 
sectional view :— 
1. Neocomian stage proper. 
2. Valangian stage and marls with Belemmites latus. 
3. Berrias limestone. 
4. Tithonian stage. 
5. Bed with large specimens of Aféychus (Kimmeridgian). 
6. Jurassic fauna with Ammonites tenuilobatus. 
The question to be settled is where, if anywhere, in this 
section the line of division between the jurassic and cretaceous 
formations is to be drawn, between 3 and 4, between 4 and 5, 
between 5 and 6, or finally through the middle of 4, dividing 
it into a jurassic and a cretaceous Tithonian. 
The Stramberg limestone, which the author regards as nearly 
identical with the limestone of the Porte de France and Aizy, 
contains §5 species of Cephalopoda, of which 50 haye been 
described as new by Zittel, whilst the other 5 have their analogues 
in the cretaceous period. This would seem to be in favour of 
the cretaceous nature of this bed ; but the Brachiopoda, which 
have been thoroughly worked out, tell a different tale: of 38 
species 26 are new, 11 belong to the jurassic period, and 1 ( Zere- 
bratula janitor, Pict.) is common to this deposit and that of the 
Porte de France. It appears, howeyer, that the strict contempo- 
raneity of these fossils is somewhat doubtful, inasmuch as Zittel 
has found that the molluscan fauna of Stramberg (omitting Ce- 
phalopoda and Brachiopoda) is nearly identical with those of 
Wimmis and Mount Saleve, which have been hitherto regarded 
as Corallian, But neither at Wimmis nor at Mount Saléye does 
Terebratula janitor occur, nor are any of the Cephalopoda of 
Stramberg found there, so that it is possible the Stramberg 
deposit consists of two beds, of which the newer contains the 
above-mentioned Cephalopods and 7Zerebratula janitor, and the 
older corresponds with the Swiss deposits at Wimmis and Mount 
Saleve—the latter might then be the highest term of the jurassic 
series, and the upper Stramberg bed the lowest of the cretaceous, 
thus carrying the divisional line through No. 4 of the aboye sec- 
tion. M. Coquand has found the fauna of Zerebratula moravica, 
which is also that of Wimmis and Mount Saléve, occupying 
deposits in Provence which are covered by beds containing 
Kimmendgian and Portlandian Ammonites, and _ therefore 
evidently jurassic. From the consideration of these facts the 
author infers that there have been in different regions two different 
orders of succession. In one (Provence, Saléve, Wimmis,) the 
stages are nearly in conformity with those which occur in the rest 
of France, and the limits of the jurassic and cretaceous periods 
appear to be clear. In the other, included between the Carpa- 
thians and Italy (with a portion of the French Alps, &c.), the 
Tithonian stage prevails upon the confines of the two great 
periods. 
By an inyestigation of the paleontology of the beds thus 
characterised as forming the Tithonian stage, Professor Pictet 
arrives at the following divisions in ascending order :— 
1. The fauna of Ammonites tenuilobatus, 
2. The fauna of the inferior Tithonian, known principally from 
Rogoznik, the blue marble of the Apennines, and probably the 
Tyrolese limestone with 7erebratula diphya. 
3. The fauna of the upper Tithonian or Stramberg limestone 
( Zerebyatula janitor). 
4. The lower Neocomian stage, especially the Berrias limestone 
( Terebratula diphyoides). 
