230 THE GEOLOGIST. j 
to form one of the levers which transmits the movements of the vacuum 
chamber to the hand. For this important improvement a prize-medal was 
awarded to Spencer, Browning, and Co., in 1862. 
Mr. Browning's aneroids possess the following advantages : — 
lat. They are most carefully corrected for temperature, from about 30° to 
100° Fahrenheit, by compound bars of metal, on the principle of the 
chronometer balance-wheel. 
2nd. They are divided by actual comparison with a Kew verified gauge, 
every inch varying in length : other makers mark an equal scale on the 
dial, and endeavour to regulate the works so that the movement shall 
correspond. Any scientific person will soon see that this is a mechanical 
impossibility. 
3rd. They have vacuum boxes made of fine hard-tempered gold, which 
impart the property to them of returning closely to their zero after ex- 
periencing a change of pressure of 16 inches. 
4th. They have the centre pivots jewelled, to diminish friction as far as 
possible : greater sensitiveness is thus obtained, and from the more accurate 
fitting of the centre staff, the instrument is not so liable to change its zero 
in travelling. 
A card, with a table of the index errors of the instrument, is given with 
each aneroid ; or the instrument will be sent to Kew for verification upon 
payment of 5^., if a fortnight's time can be given. 
When an aneroid has changed its zero, it has been customary to correct 
it by turning a screw at the back of the instrument, which acts through the 
medium of the mainspring on the vacuum chamber. 
This, however, is attended with two rather serious objections : — 1st, it 
alters the tension of both the mainspring and the vacuum chamber, which 
do not settle down for some time ; and, 2nd, it alters the range of the whole 
instrument. 
These objections can now be obviated by a beautiful but simple contri- 
yance, suggested to Mr. Browning by Francis Gralton, Esq., F.E.S, This 
consists in making the dial turn round on the barometer case. By this 
arrangement the instrument is readily corrected by turning the dial until 
the required division comes under the pointer. 
These aneroids should be held in a horizontal position while being read, 
and not tapped previous to taking an indication. 
Tektiaey Mammalia and Shells. — The Tertiary beds of Madrid 
contain, according to Messrs. Sullivan and O'Reilly, bones of Anoplothe- 
rium Paleotherium, Antelope, Cervus, Sus, Rhinoceros, Hippopotamus, 
Mastodon. The Tertiary dolomitic limestone near Guadalaxara is often 
completely full of the sheUs of LimncBa planorUs, Faludina, Helix, etc. 
Eeeata in Fossil Birds. — The following corrections in the references 
to the Plates require to be made :— At pagelS, line 12, /or " see PI. IV.," 
read see fig. 2, PI. III. ; line 13, after (" fig. 115 ") insert see PI. lY. 
fig. 3; at page 23, second line from bottom, /or "PI. V.," read PI. XIL 
It will be desirable, throughout the entire series of papers, to refer to the 
figures in the Plate by the notations given in the Explanation of the Plates 
at page 233, rather than by those given in the articles, as some errors have 
occurred. — S. J. M. 
Errata.— Page 87, last paragraph, /or R. TJngeriana; and Eeuss's 
R. ammonoides," read " R. Ungeriana, and Eeuss's R. ammonoides ;" it 
not being intended to hken the last to R. Akneriana next mentioned. 
