WITH NOTES. 503 



[A conceited Door. ] Van Etten, in his Mathematical 

 Recreations, offers as Problem XV. u How to make a 

 Door or Gate, which shall open on both sides.&quot; It is 

 represented that &quot; All the skill and subtilty of this, 

 rests in the artificiall disposer of four plates of iron.&quot; 

 The description, which is very imperfect, concludes 

 &quot; the gate will open upon one side with the aforesaid 

 plates, or hooks of iron ; and by the help of the other 

 two plates, will open upon the other side.&quot; [Oughtred s 

 ed. 1653, page 30.] The Marquis may have conceived 

 his own plan to be a most decided improvement upon 

 this primitive design. 



75- 



How a Tape or Ribbon-weaver 5 

 may fet down a whole difcourfe, 

 without knowing a letter, or inter 

 weaving any thing fufpicious of 

 other fecret then a new-fafhioned 

 Ribbon. 6 



5 riband- weaver. P. 8 riband. P. 



[ A Discourse woven in Tape or Ribbon. ] This article 

 should have followed article No. 43, of which it seems 

 to be one of the &quot; variations&quot; therein contemplated. 



7 6. 



How to write in the dark as 

 ftreight as by day or candle-light. 



[To write in the dark.~] This would appear only to 

 require a box of any form, the top or lid of which being 

 of ground glass, it could be illuminated by means of a 

 small night-light placed below, within the box ; when 



