36 Connection beliceen Geology and A(jricullure. 



same author sug-gests that, though unquestionably the beneficial 

 effects of this mineral manure depend on the presence of the cal- 

 careous matter, the sea salt with which it is impregnated contri- 

 butes materially to its fertilizing powers ; citing as a fact, bearing 

 strongly in favour of this opinion, that the farmers send several 

 miles to the harbour of Padstow for the sand* which is drifted close 

 to them.y The farmers certainly seem to prefer the sand which 

 the tide has just left, and which must consequently contain much 

 saline matter. It often also then contains fragments of sea-weed, 

 and occasionally fresh animal matter derived from dead marine 

 creatures, among which are the tenants of microscopic shells still 

 little decomposed in them. 



V. — Ohservations on the Wheat-niidge. By the Rev. J. S. 

 Henslow, Professor of Botany in the University of Cam- 

 bridge, and Rector of Plitcham. 



The contribution which I now offer towards elucidating the 

 history of the wheat-midge is so very slight, that I should scarcely 

 have ventured to forward it to any other publication than a 

 journal expressly devoted to the progress of agriculture. It is 

 chiefly with the hope of stimulating others to co-operate in observ- 

 ing the habits of this little pest that I have determined to do so. 

 I have been disappointed in not ascertaining the precise circum- 

 stances under which the larvae of this gnat pass to the state of 

 pupae, and these again to the fly state. Until these circumstances 

 are explained. Me cannot feel perfectly sure that any proposed 

 palliative against their attacks is likely to be of essential service. 

 I shall detail the observations and experiments which I have made 

 since last year ; and if they have no further benefit than showing 

 the possible extent of damage which this insect is likely to pro- 

 duce in seasons favourable to its increase, an effort will have been 

 made towards provoking practical men to a more attentive study 

 of its habits. 



* The writer of this note was informed by a gentleman at Padstow that 

 the freshest sand of that harbour contained more than 8 per cent, of 

 carbonate of lime. It would be very important to know in what proportion 

 the alk'aline and earthy muriates and sulphates known to exist in sea-water 

 are contained in this sand, as there can be no doubt that the value of this 

 sand as a manure depends almost entirely upon its saline contents, which 

 may be applied to land where the sand cannot be obtained. They constitute, 

 in fact, an essential part of all perfect manures. — F. Falk^jer. 



■\ Trans. Geol. Society of Cornwall, p. 194. Borlase has observed that 

 the Salter the sand the bettor it was for agricultural purposes.— (Nat. Hist. 

 Cornwall, p. 82.) " Blown sand," he says, "which has been long exposed 

 to the air, is good for little, its salts are so wasted bv wind and rain." — 

 {Ih. 83.) 



