36 



Methods of estimating accurately 



feet 2 inches across the wings. It is an old one too, for the 

 teeth are well mumbled or worn down. 



Seeing that bats are condemned to hang ever head down- 

 wards, it is not an impertinent question to ask how they 

 void their excrement, without interfering with their own 

 persons. This is minutely explained in Geoffroy's Cuvier, 

 Mammalia, vol. ii. page 95. The Pteropus goes through the 

 same ceremonies precisely as the bats described in that 

 publication; viz. when urged by the call of nature, it 

 adroitly reverses its position by hanging on with the thumb 

 claws and letting go its feet, when of course, with reference 

 to its own head there is no further occasion for the precau- 

 tion. 



Since commencing this paper, of five I had in captivity, and 

 from which most of these remarks are taken, but one re- 

 mains, two died of their wounds ; one of decline, (although it 

 ate ravenously to the hour of its death ;) one flew away. The 

 remaining one is in good condition and perfectly tame. They 

 were very quarrelsome when together, and frequently bit 

 and wounded each other severely. The animals are cruelly 

 infested by a tough nimble spider-shaped tick (Oribata Ves- 

 pertilionum,) which the most incessant scratching fails in 

 getting rid of. 



Methods of estimating accurately the Substances usually present in 

 Water. By Mr. A. Robertson, Calcutta. 



Before describing these processes, it may be of service to mention 

 something about the vessels to be used, and the manipulation. The 

 quantity of water ought to be determined by weight, as being much 

 more accurate than measurement, and 10,000 grs. is a very conveni- 

 ent portion for the purpose. To concentrate this by evaporation, a 

 wedgewood-ware basin, usually recommended, is rather improper, on 

 account of the difficulty of excluding dust from it, and the porosity of 



