146 



which might now be done with facility, a work which will task the critical 

 skill of the most experienced observers. 



Perhaps I may be permitted to add a word of caution : — there is some 

 danger of attaching too great importance to the rapid spread of plants in 

 certain localities, as evidence of their exotic origin : for example, Gypsophila 

 tubulosa, and Polygonum avicidare, are regarded as introduced chiefly on this 

 ground. But truly native plants as Microloena stipoides, and Danthonia semi- 

 annularis, have increased in an equally remarkable degree in the northern part 

 of this province during the last four or five years, and have evinced a 

 surprising power of adaptation to altered and altering circumstances, beyond 

 having become plentiful in undisturbed localities where they were formerly 

 scarce. Facts of this kind, however startling in their nature, and obscure in 

 their origin, are of high significance and importance in their relations, and 

 show most forcibly the impolicy of adopting sweeping conclusions, and the 

 necessity for patient and continuous observation. 



Comparative statement of the position of the species enumerated in 

 the foregoing catalogue : 



Denizens . . . . .109 



Colonists . . . . Ill 



Aliens . . . . .31 



Extinct and Erroneous . . 12 



Probably Indigenous . 9 



Position not known . . 20 



Total . . .292 



III.— C II EMI ST RY. 



Art. XXVII. — On the production of certain Crystalline Phosphates and 

 Arsenates. By W. Skey, Analyst to the Geological Survey of Xew 

 Zealand. 



[Read before the Wellington Philosophical Society, February 9, 1869.] 



A great many minerals occur in a natural state, which, in their chemical 

 constitution, their crystalline form, or both combined, have not yet been 

 artificially produced. 



It seems very desirable to know, both upon chemical and geological 

 grounds, the conditions necessary for their production, and especially in 

 those forms which they assume in nature. 



The metallic phosphates and arseniates — a group of salts which, almost 

 without exception, are only known in the laboratory as gelatinous or pul- 

 verulent precipitates, — stand conspicuous among those native minerals, which 

 we have hitherto been unable to obtain by artificial means in their crystalline 

 forms. 



I have recently attempted the crystallization of some of these compounds, 

 with a certain degree of success ; and further, in the course of my experiments, 

 I have succeeded in crystallizing some phosphates, which, hitherto, have not 

 assumed such a crystalline form, either naturally or artificially. 



