196 Transactions. 



(5) using H as centre, describe a quadrant HK of radius HQ ; (6) join K 

 to P by a straight line, thus completing the cam-contour. 



This simple curve falls slightly within the true cam-curve for a portion 

 of its length, biit so slightly as to cause a maximum error of only about 

 1 per cent, in the virtual length of the short arm of the balance. In the 

 example given this amounts to less than \ mm. This makes no dii?erence 

 to the perfect accuracy of the balance ; it only makes a slight difference 

 in the perfect equality of the distances between some marks on the scale. 



All need of levelling the balance when it is stood upon any nearly level 

 surface can be avoided by suspending the scale so that it can itself assume 

 the correct position by the action of gravity. 



A very simple and effective anti-parallax sight is fixed to the pointer. 

 This consists of a needle having an enlarged eye, through which the observer 

 must look at the pointer, and thus note the point it indicates on the scale. 



The cam lever, the swivelled scale, and the anti-parallax sight combine 

 to produce a balance of surpassing excellence for accuracy and speed of 

 measurement. This invention the aixthor presents to the society in the 

 hope that some one will be sufficiently enterprising to j)ut it upon the 

 market, to the great advantage of himself and the public at large. 



Akt. 'KNlll.— Description of a New Native Grass (Poa). 

 By D. Petrie, M.A. 



[Bead before the AucMand Institute, 22nd Noveniber, 1909.] 



Poa oraria, sp. nov. 



Gramen csespitosum, parce foliosum, 40-50 cm. altum, leve, politum, 

 perenne. 



Culmi multi, erecti, glaberrimi, graciles, a basi ramosi, teretes, 2-nodosi, 

 internodiis elongatis, folia longitudine eequantes, foliormn vaginis psene ad 

 imam paniculse partem vestiti. 



Folia longe vaginantia, vaginfe inferiores lat?e, membranacefe, stra- 

 mineae, leviter striatse ; ligula vaginam latitudine sequans, oblonga, obtusa ; 

 lamina teres, erecta, involuta, subrigida, gracillima, leviter striata, apice 

 subacicularis. 



Panicula strictissima, linearis, + 10 cm. longa ; ramis 3 v. paucioribus, 

 brevibus, teretibus, glaberrimis, paucas spiculas sublonge pedicellatas 

 gerentibus. 



Spiculae anguste oblongse v. plus minus cuneatse, 8 mm. longse, 3 mm. 

 latse, 4 V. 5 flosculos gerentes. 



GlumfB vacufe subsequales, spiculis tertia parte breviores, anguste 

 lineari-lanceolatfe, acuminatse, 3-nervat8e. 



Glumse floriferse anguste lanceolate, acuminatee, membranaceae, plerum- 

 que 5-nervat8e, nervo medio solo ad apicem attinente, basi parvo pilorum 

 brevium flocco prsedita, in nervis subsericeae, alibi plus minus scabridae. 



Palea gluma florigera paulo brevior, 2-nervata, nervis delicatide ciliatis. 



Hah. — Moist and wet stations at the head of several of the sounds of 

 western Otago (Deep Cove, &c.). Collected by Mr. B. C. Aston in mid- 

 January, 1909 ; it appears to flower towards the end of December. 



