478 PHILOSOPHICAL TRANSACTIONS. [aNNO 1681. 



Of a Flying Ship* By Fr. Lana, Philos. Collect. N°l, p. is. 



But no one yet thought it possible to make a ship which should pass through 

 the air, as if it were sustained by the water, because they have judged it im- 

 possible to make an engine which should be lighter than the air, which is, 

 nevertheless, necessary to be done in order to produce this effect. But I hope 

 at length I have fallen on a way of making such an engine as shall not only_, by 

 its being lighter than the air raise itself in the air, but together with itself buoy 

 up and carry into the air men, or any other w^eight ; which I confirm both by 

 certain experiments, and by geometrical demonstration. 



I suppose first, that the air has weight, because of the vapours and exhala- 

 tions, which are raised from and incompass our terraqueous globe to the height 

 of many miles. And the proof of it may be made by evacuating, if not all, yet 

 a great part of the air out of a glass-vessel, which having been first weighed, 

 and after the extracting of the air weighed again, will be found notably lessened 

 in weight. Now how much the weight of the air is, I have found in this man- 

 ner : I took a large glass vessel, the neck of which could be shut and opened 

 by a stop-cock ; and being open I heated it at the fire, so that the air in it be- 

 ing rarefied, issued out of it in great part : then I suddenly shut it, so that the 

 air could not re-enter, and weighed it : which done, I sunk the neck under 

 water, the body of the glass remaining all above the water; avid opening it, the 

 water ascended into the glass, and filled the greater part of it. Then I opened 

 it again, and let out the water, which I weighed, and mea5>iired the bulk and 

 quantity thereof. Whence I inferred, that so much air had issued out of the 

 glass, as there was water that had entered to fill the part left by the air. I 

 again weighed the vessel, first well wiped dry, and I found that it weighed an 

 ounce more whilst it was full of air, than it did when the greater part of it was 

 evacuated. So that that surplus of weight was a quantity of air, equal in bulk 

 to the water that had entered into the place of it. Now that water weighed 

 640 ounces : whence I conclude, that the weight of the air, compared with 

 that of the water, is, as one to 640, that is, if the water which fills a vessel 

 weighs 640 ounces, the air filling the same vessel weighs one ounce.-j^ I sup- 

 pose, secondly, that a cubic foot of water weighs 80 pounds, or 960 ounces ; 

 for I found that that water which weighed 640 ounces, was little less than -f- of 



* This account is extracted and abridged from the 6th chapter of Fr. Lana's book called 

 Prodromo. 



t This method of finding the relative weight of air, in respect of that of water, is ingenious 

 enough ; though the experiment here described has not been accurately performed, since instead of 

 640 times, it is now well known that water is 830 times heavier than air. 



