Proceedings of Societies. 
245 
1829.] 
ter of the two to overcharge than undercharge the proportion of the salts to the 
water. It will be apparent, for obvious reasons, that the part containing the sub- 
ject to be cooled should be as thin as may be, and the whole of the external part in 
every apparatus, thick. 
This detail may probably appear prolix to any person induced by curiosity only 
to look it over ; but to any one who means to put it in practice, the whole will be 
found essential, and with a little attention and experience become familiar and easy, 
and which I have endeavoured to combine every advantage the subject will admit 
of; and as coming from the “ fountain head,” it may not prove uninteresting to 
some at least of your numerous readers. 
I am, Gentlemen, 
Your most obedt. servt. 
0 . rfurd , April 28 th , 1828. Richard Walker. 
The following remarks are contained in a second letter, published in the July 
number. 
The drier and finer the mixed powder of sal ammoniac and nitre is, the better; 
and the pulverisation is best effected, in the first instance, with a heated pestle. 
Glauber’s salt in an efflorescent state, or which by long keeping or from access of 
air has changed to powder, is unfit for the purpose; in this state producing heat by 
solution in water. The best way of preparing the frigorific mixture is by previous- 
ly placing the powdered Glauber's salt, and giving it a level surface, at the bottom 
of the vessel, and upon that the mixed powder of sal ammoniac and nitre ; adding 
first about half the quantity of water, and immediately after the remaining portion, 
stirring the whole together each time. The vessel containing the powdered salts, as 
above stated, may remain thus any convenient time before adding the water. (Care 
must be taken to stir the evaporating mixture towards the end of the process, and 
not to urge it top far.) Nitre being a much cheaper article than sal ammoniac, 
more easdy reduced to powder, and producing about 18 degrees of cold by solution 
in water, may supersede the use of the mixed powder for cooling the water in which 
wine is placed. This powder, moreover, is useful, occasionally, as an addition to 
mixtures of ice and salt, to increase the power and accelerate the process. 
The proportions of the articles given in my former paper are adapted to the tem- 
perature of 50° ; at a higher temperature, of course, the water w ill dissolve a some- 
what larger portion of the salts, and the effect will be proportionably greater. Thus 
the most powerful mixture, given in my table of frigorific mixtures, consisting of 
phosphate of soda, nitrate of ammonia, and diluted nitric acid, will, when mixed 
at the temperature of 50°, produce a cold of 21° below 0° ; and if mixed in due pro- 
portions at 100°, it will produce, in an instant, a cold of 20° ; viz. a reduction of 
eighty degrees. By means of this mixture, as I have been informed, water has 
been frozen solid “ under the line.” 
IV . — Proceedings of Societies. 
1. Asiatic Society. 
A Meeting of this Society took place on Wednesday, the 1st July, the President 
in the chair. The Count de Nob was elected an honorary member, and Captain 
MacDougal, Mr. Baillie, and Baboo Kasinath Mullick, were elected members of the 
Society. 
The President informed the Society, that Lord William Bentinck had consented 
to become the Patron of the Society. 
Letters were read from Dr. Tytler, Mr. Montgomerie, and Mr. Allan, requesting 
their names to be withdrawn from the list of Members of the Society. 
The circumstance of Dr. Tytler' s secession led to a resolution, that a letter should 
he addressed to that gentleman expressive of theS r ciety's regret at his secession, 
and of the sense entertained by the Society of the zeal he had always manifested for 
its interests. 
A letter was read from Mr. Colder, announcing the realization of his Majestythe 
King of Unde's splendid donation to the Society of twenty thousand rupees, and al- 
so of a donation of five thousand rupees from his Majesty’s Minister, Yatimad-ud- 
Dowla. The full amount of both these donations has been remitted by Mr. Ricketts, 
the Resident at Lucknow, who had handsomely made up a considerable loss by the 
exchange, which would otherwise have fallen on the Society. 
