24 PROFESSOR CONNELL ON A 



When the air is very moist, and there is little difference between the tem- 

 perature of the air and the point of deposition of moisture, care may be taken 

 that the ether shall have a temperature some degrees above that of the air, 

 which will be effected by holding the hand for a little on the brass bottle 

 after the ether has been introduced into it, or by employing any other means 

 likely to accomplish this object. 



If an observation should at any time be made entirely out of doors, all that 

 will be necessary will be to have some fixture attached to a tree or gate-post, or 

 inserted in the ground, to which the clamp may be secured. 



Messrs Kemp have undertaken to prepare the apparatus with clamp, bottles 

 for ether, &c. &c, packed conveniently in a small portable case ; and any one 

 who may procure it from them, or from an} r other instrument-maker, ought, of 

 course, to take care that all the particulars mentioned in the foregoing observa- 

 tions are rigidly complied with. Insufficient or careless workmanship is quite 

 incompatible with success ; and as already stated, it is not only necessary that 

 the instrument shall be of extremely good construction at first, but that it shall 

 be preserved in that state, in all points. In its present state it may seem very 

 simple, as I am happy to say it really is, but still the result was not attained 

 without much consideration regarding minute particulars on my own part, and 

 skill and dexterity on the part of the artificers. It is with the view of enabling 

 others to construct the instrument efficiently, as well as to think of remedies 

 for any other difficulties which may occur, that I have allowed myself to indulge 

 in so much narrative and detail of particulars. 



I think that it may be found that the instrument will have the advantage of 

 being little liable to accident in travelling, and the thermometer is very securely 

 packed in a proper case. 



I should be very sorry to have it thought, that in any observations which I 

 have made regarding Mr Daniell's hygrometer, I should be supposed to speak 

 in the slightest degree in a tone of disparagement of that instrument. On the 

 contrary, I think that I have shewn that, with a slight allowance, it is perfectly 

 trustworthy ; and I firmly believe that so beautiful and philosophical an instru- 

 ment will never be entirely superseded. If that which I have described shall 

 ever be thought to have an advantage over it in any respect, it will, I think, be 

 on the score of little tendency to injury, and probably to greater facility of obser- 

 vation, after a little dexterity of manipulation has been acquired by practice. 

 There is undoubtedly an occasional difficulty in noting the results by Daniell's 

 instrument. I must, however, take the liberty of repeating my protest against 

 a view which I fear there is ground for thinking some English meteorologists 

 have quite made up their minds to adopt, that the indications of Daniell's hy- 

 grometer are quite accurate, and ought to be taken as the general standard of com- 

 parison, according to which the accuracy of all other dew point instruments, and 



