34^ Memoh' en the Vropertifs of Yiiria Earth 



pole confequenlly drawn proporiionably upwards, that the 

 itring ot the valve will bf olherwife out of the traveller's 

 reach; an accident which has frequently obliged them to 

 climb up into the netting io regain it. The valve itfelf 

 fiiould be covered with foft leather, reaching an inch or two 

 beyond its edge every way. It? litualioii fliould be upon 

 the equator*, (and not, as generally directed, near the top,) 

 elfe the lightefl gas will be that which will efcape; not to 

 mention alfo the greater inconvenience in the latter cafe, 

 arifing from the eftablifliment of a complete current of atmo- 

 fpheric air through the balloon bv the neck and valve toge- 

 ther (the neck being generally left open a few inches), where- 

 by a quantity of the lighter gas is carried off greater than one 

 would imagine. To obviate this, the neck and valve (hould 

 never be both open at one time ; and I apprehend the acci- 

 dents frequently occafioned by the ufuallv rapid defcent and 

 rebounding of a balloon, are to be attributed to an inattention 

 to this precaution; the gas being viokully carried out of the 

 valve by a current of air running through the balloon, and 

 this current increafing with the velocity of the defcent; fo 

 that, when the valve is again clofed, the balloon is found to 

 have decreafed in levity much more than was wiflied for. 



The car for balloons may be left to the option of the ama- 

 teur, remembering that light weight, and the property of 

 floating if defcending over water, be attended to. 

 [To be coniinued.} 



LVII. FiXtraSi from a Memoir on the Properties of Yttriii 

 Earth compared luith thofe of Gluciiie; on the Foffth in 

 luhich the former of thefe Earths is contained ; and on the 

 Difcovery of a nezv Subjlance of a Metallic Nature. By 



A. G. EKEBERGf. 



X HE firft part of this memoir contains an account of 

 fonie pxpf riments, made by M. Ekeberg, to eftablifli the 

 difference between glucine and the earth difcovered in the 

 gadolinite, and called yiirca or gadolinc ; but as the pe- 

 culiar nature of each of tliele eardis is already well known 



■^ The openint; of :he valve bL-ui;; f imetimes required durrng the rapid 

 .ifcenfion of a balloon, and bcir.st followed alfo by a quick defcent, the 

 equator is pointed out as the moft proper iituation in which to place tha 

 ■fijve, to prevent the atmofphcric :iir fiom rulhlng in either cafe into the 

 h.; I loon. 



+ Vmxn the Tranfaifri ens of I kf Acau'emy cf Srirvrrs "i S'-'l-'-l"' for 

 j^'o:, firft quarter. 



to 



