AA REPORT—1868. 
Analysis of the Roman Mortar from SL. Tower, Burgh. 
ie 
SHUG a seas aba do SOG US bio US Sih . 54:50 
Solulbletoiltcam meters) ssoisede a lene oieeens 0-40 
Red brick with some unburnt clay ...... 18-00 
Gambon ate ronellnehsiess: ede eaocone tks Loess cle 25:°75* 
Se ep ATA OMe yeu stePous ce eiceiece ine asters 0-15 
Carbonate of magnesia.............s100. 0:08 
Cio oaochiiiat Gamagmacanedoo dual od 0:05 
Magnetic oxide of iron , 
WW ogdcharcoal DAdomapasoo ss a8 traces 
Water, chiefly hygroscopic .............. 0:92 
ICAI E Soran doons ine eovgo ondn ea se 99°85 
Other Samples of Burgh Mortar. 
I,» SLU ae 
Sand and brick, with a little unburnt clay .. 72°3 71:4 67:0 
Carbonate of lime, &e. (by difference) ...... 27°77 286 35:0 
Samples II. and III. were taken from the south wall; specimen IV. from the 
north wall. 
Red Brick, or Tile, from S.E. Tower, Burgh. 
Silicaperbeat sce tee eerie ie noche tae (27 
AVomnimia: 2. sci Ah EP ceOtucnee sich atic 14:0 
Peromdejoriron.: Geel eee walen e cs 10:0 
1 By es Tian MCRD Cree aa ony ate Cee ea oe oka 21 
Maenesia fe 
@xideyoramencamese (0 rRES 
PAlicnTestum LOS sivas ss cea cake nig Fe eS ee, 
100-0 
On the Absorption of Gases by Charcoal. By Dr. R. Anevs Surra, RS. 
The author said that he had somewhat further extended his inquiries into the 
laws of absorption of gases, as shown by charcoal. Ile had some years ago said 
that he believed the actions were on the border between chemistry and physics, or 
that physical phenomena were an extension of the chemical. Last year, in a short 
note, he stated that the gases which he tried were absorbed in whole volumes, or 
volumes which were multiples of hydrogen. He had now tried other gases, with 
the following results:—Hydrogen, 1; oxygen, 7°99; carbonic oxide, 6-03; carbonic 
acid, 22:05 ; ‘marsh-gas, 10-01; nitrous oxide, 12-90; sulphurous acid, 36° 95 : com- 
mon air, 40-063. Nitrogen was found to be 4: 27; probably this is a little too low, 
as there is always some nitrogen left in the heated charcoal. These numbers are 
got by dividing the number of volumes absorbed by each gas by the volumes of 
hydrogen absorbed. They are an average of many experiments. The numbers in 
some cases differ considerably ; it is supposed that the reason lies in the constitu- 
tion of the charcoal, but it may be partly owing to the mode of working. 
He considered that the ultimate particles of gas rested as strata or lay ers in the 
charcoal ; the outer particles were therefore less forcibly held than the more dis- 
tant. ‘The latter were also most difficult to remove. If’ this physical action had 
an analogy with chemical action, it would probably throw {light upon it, and it 
seemed to point to compounds containing parts held together more or less loosely 
than other parts. The gas and charcoal form such a compound, which in asense is 
not purely chemical 
Two of the numbers seem to be very remarkable; namely, those of oxygen and 
carbonic acid, as the volumes are exactly those of the weights ofoxygen in water and 
of an atom of carbonic acid. Eight volumes of oxygen are 128 times heavier than 
* Found, lime 14:5, carbonic acid 11-25 per cent. 
