Notices to correspondents. 



We have received our Correspondent A's Letter from Rome, and shall be glad 

 to hear ngain from him when he returns to Scotland. 



Mr E.'s Essay is too elaborate for our pages, and is more suited for a Medical 

 Journal. 



We would recommend it to M. to send his Model to the Society of Arts for Scot- 

 land, which holds its meetings twice every month in the Royal Institution. If it 

 merits it, it may appear at the General Exhibition 'of inventions, which is to take 

 place in May 1827. 



We shall be happy to solve the difficulties mentioned by our Bristol correspond- 

 ent so far as we can ; but we cannot undertake to be expounders of scientific riddles. 



M. D.'s observations on Vision cannot be inserted. If he will give us a personal 

 interview with him, we shall demonstrate to him the fallacy of his experiments. The 

 papers to which he alludes are certainly full of experiments and observations ; but they 

 are bad ones. Nature may be interrogated by a thousand and one experiments, and 

 yet m ay not give a response worthy of being recorded. 



We have received J. G.'s observations on the Mean Temperature of the Earth, 

 containing new formula? for determining the mean temperature of different points 

 on the earth's surface. The author has committed a mistake in considering the mean 

 temperature as an angle , of which he gives the sine and cosine. Owing to the acci- 

 dental circumstance of the polar temperature being not far from 0°. and the equato- 

 rial temperature above 80°. in Fahrenheit's scale, the formulae give tolerably correct 

 results ; but if he uses the Centigrade scale or Reaumur's, he will find that his for- 

 mula; are entirely inapplicable. We shall be glad to receive J. C.'s Meteorological 

 Journal, or an annual abstract of it, as it promises to be a valuable one. In answer 

 to J. C's query, we beg to state that correct indications cannot be obtained from 

 hygrometers in frosty weather. Captain Parry found that with Daniell's hygrome- 

 ter he could never obtain a deposit on the back of the instrument, below an atmo- 

 spheric temperature of -f-6 . of Fahr. 



Mr Nasinyth's description of an instrument for measuring the comparative expan- 

 sibility of metals, W ill appear in our next number. 



Mr Scouler's paper on the temperature of the North West Coast of America, will 

 appear in next number. 



Our Correspondents are earnestly requested to transmit their Communications to 

 the Editor before the 10th of March, the 10th of June, the 10th of September, and 

 the 10th of December. 



