270 Miscellaneous. [May, 
by means of a pedal the damper that usually covers them, the sound will be dou- 
bled by the reciprocal vibration of the extra strings : the thought has much ingenui- 
ty, and all that can be urged against it is that the bulk of the instrument is some- 
what increased, and with it the chances of derangement and getting out of tune. 
4,—Specifie Gravity of Metallic Alloys. 
In the second number of Brewster’s Journal N. S. are some curious results 
obtained in experiments on the melting points and densities of different alloys, by 
M. Kupffer. It appears that in every proportion of tin and lead from one of tin 
with one of lead, to one of tin with four of lead, and from one of tia one of lead to 
six of tin one of lead, there was expansion, i. e. the specific gravity of the alloy was 
found to be less than that given by calculation. At two of tin one of lead, and still 
more at three of tin one of lead, the difference was trifling ; and as the difference in- 
creased each way it was conjectured that at some intermediate proportion between 
those two, the resulting specific gravity would agree with the calculation. It was 
found that one volume of lead to two of tin gave a specific gravity almost exactly 
that of calculation. 
In amalgams of tin and mercury, again, contraction was found to take place ; it 
being null when one combining volume of tin was added to two of mercury. In 
amalgams of lead and mercury the least contraction is found when one combining 
volume of lead.is united to three of mercury. 
The following melting points were observed : 
Centigrade Fahrenheit. 
JEGE Wen CIN IACI IC CCNCL CREO mt iii: PIE. Dh. SBT 63%.2 
UT ee He ema Se OcIp aa0 CO Ore mniGat OC Of viatt -. 230 466 
Tin 5 primes, Lead 1 ‘prime, pales ete! ou d.k wuetayate 194 34G.2 
brs s Navapieys $e setre eee OD $62,u 
By hep ides MO rae esters ne eo 356.8 
Di rise a ; F 6.6196 3e¢.F 
ee Deeds = . 241 WEI 
Teas EE Ye MbLEE SSO ROR CRS 289 GFL, 
2 volumes, 1 volume,. exes 194 DiS ee 
These temperatures were determined iy noting the Een of mercury driven out 
of a small bulb furnished with a capillary tube, in the same manner as practised by 
Messrs. Dulong and Petit. They will therefore require some correction. D. 
5.—Proportion of Recent and Fossil Shells. 
The following notice of the numbers of known species of recent Testaceous 
Mollusca and of Fossil shells is taken from Loudon’s Magazine of Natural History. 
es 
Simple Piva Multilo- 
unival- |and mul-jcular Total. 
ves tivalves. |univalves 
Testaceous Mullusca of the present world,| 1961 874 08 2893 
Species of British Fossil shells, ........ 401 634 230 1265 
Of the 1265 Fossil Species, the following is the distribution. 
Ist Division, 1st Section, Carboniferous | 
order of Mr. Conybeare, ............ 27 | 80 33 | 140 
‘Ist Division, 2nd Section, to the Lias in- 
CIUSIVEN (oe Wis tic e ccntcaeRetis catty beter cseiate 9 38 50 97 
2nd Division, from the Lias upward to the 
Chalk inclusivess stad ce elie thee ste 106 375 139 620 
3rd Division, Tertiary Beds above ae 
LY AR ye a siel'sislalesai AAW tee 259 141 | 8 408 
