Proceedings of the Royal Society of Edinburgh. 193 



The conclusion at which he arrives is, that the Newcastle lens is 

 scarcely inferior to the lens made in Paris ; and that the IMessrs Cookson 

 are undoubtedly entitled to the merit of having successfully combat- 

 ed the difficulties which attend the making of polyzonal lenses in 

 one ■ piece, — difficulties previously considered insurmountable, but 

 which they have overcome at the first attempt. The author expects 

 that some of the particulars of the method by which they effected 

 their purpose will be communicated to the British Association at their 

 meeting at Edinburgh in September next. 



March 3. — Sir Thomas Makdougall K. C. B. President, 

 in the Chair. The following communications were read : — 



1. On a New Register Anemoscope. By Dr Traill. 



The author's object was to obtain an instrument which might re- 

 gister the changes of the wind in the absence of the observer. For 

 this purpose he connected a vane with a vertical axis, at the lower end 

 of which the horizontal revolution was changed to a vertical revolution 

 by bevelled wheels ; and the axis of the vertical wheel carried an index 

 and pencil ; which described on a vertical dial of slate, or of polished 

 porcelain, all the changes experienced by the vane above. In this man- 

 ner, however, the instrument registered the changes occurring during 

 only one revolution of the vane. In order to obtain the registration of a 

 greater variety of changes, — when the wind has blown all round the 

 compass more than once, the following addition was made. "Each bevel- 

 led wheel containing 42 teeth, a pinion of 21 leaves was fitted to the 

 axis of the vertical wheel, which pinion plays in the teeth of a small- 

 er wheel with 42 teeth also provided with a pinion of 21 leaves. 

 This last moves a second small wheel of 42 teeth, which again turns 

 round the axis of the primary vertical wheel. The last small wheel 

 moves a second index which turns round the dial-plate once, while 

 the vane and primary index make four complete revolutions. The 

 second index carries a stud, which moves in either direction a pair of 

 hands concentric with the indices, but not attached to their axis. 

 This stud, then, will carry one of the hands through 90 degrees, while 

 the vane has made one complete revolution ; or the hands are capable 

 of indicating four entire revolutions of the vane. The face of the in- 

 strument has three concentric graduations. The interior is the 

 rhumbs of the mariner's compass ; the second has the degrees of a cir- 

 cle ; and the outer scale has four series of 360 degrees." 



2. On the force of the Latin Prefix ve or vae. By the 

 Rev. John Williams. 

 March 17.— James Russell, Esq. Vice-President, in the 

 Chair. The following communications were read : — 



1. Notice of Experiments on the Diminution of Intensity 

 sustained by the Sun's rays in passing through the Atmo- 

 sphere. By Professor Forbes. 

 This subject, though in itself deeply interesting, and leading to 

 conclusions of much importance for elucidating many obscure ques- 



VOL. XVIII. NO. XXXV. — JANUARY 1835. N 



