348 PHILOSOPHICAL TRANSACTIONS. [anNO 1687. 



Statue, not above a foot or two high, whose mould may be managed in the hands, 

 then I make a concave statue of wax of the thickness desired, and place upon 

 it all the great and small channels as before, which done, I put it all together 

 into a liquid substance, made of plaister and tile or brick-dust tempered with 

 water. 



If the statue be intended very thin, I take copper, and when it is well melted 

 I mix with it a good quantity of zink, the more, the better the metal runs. I 

 have sometimes for small and thin statues put in above a third part of zink, and 

 I have found by experience that this mineral makes the metal run more freely, 

 and gives it a fair golden colour. 



The statue being cast, I take off the mould, and cut off all the little channels ; 

 all which, both great and small, are filled with metal, which may be kept for 

 further use ; in these there is much more metal than in the whole statue ; for if 

 the statue be very thin, there must be more and larger channels ; and so the 

 cheaper the statue the more weighty the channels, and the more metal remains. 



To know the quantity of metal requisite for my intended work, I take a 

 lump of the same mixture of wax and pitch, with which I make the mould of 

 my statue ; and having weighed it I make a mould upon it, and cast in the same 

 a lump of metal of the same size, which I weigh, and thereby compute the 

 proportion of the weight of the metal and wax ; then observing how many 

 pounds of wax I use about the figure and channels, I can calculate nearly how 

 much metal I should melt. 



The Answer of Dr. Papin to several Objections made by Mr. Nuis against his 

 Engine for raising Water by the Rarefaction of the Air, of which a Descrip- 

 tion is given in N° ITS of these Transactions. N° 186, p. 263. 

 Those objections were in the Nouvelles de la Republ. des Lettres of the 

 month of December last. 



In the first objection Mr. Nuis says, that it would be a very hard matter to 

 hinder some receptacles from being filled too much. To this 1 answer, that it 

 being necessary to let out the water of the highest receptacle, I thought it might 

 be conceived that the water may also be let out of the inferior receptacles by 

 inserting into each of them a crooked pipe, reaching a certain way downwards, 

 and having its lower aperture shut up with a valve, by which the water might 

 run out when the receptacle should be filled to a certain height. 



The second difficulty lies in the great quantity of air to be rarefied. Mr. 

 Nuis, by his computation, finds that the pumps should every one contain 84 

 cubic feet of rarefied air to raise water at 12000 feet distance. Let the distance, 

 as he supposes, be 12000 feet, and the capacity of each receptacle about \ cubic 



