The merit of this improvement
account of small differences in the focal lengths of the lenses attached to the instrumentIn order to bring all the traces to a uniform and convenient standard, they are severally reduced by Mr. Ga]ton’s pantagraph p. 30, which reduces in length and breadth, independently. By its means they are considerably compressed, and their vertical scales are rendered unifor The style of this pantagraph is a steel cutter, which scratches the reduced copies deeply into zinc plate A single zinc plate is allotted to each day at each statio The barogram and two thermograms are cut on its obverse, with fiducial marks attached, and the wind’s direction and velocity are cut on its reversThe wind velocity trace is divided by means of the same pantagraph into hourly sections, starting afresh from the same base linea plan which affords a more useful and intelligible representation than the original recor is due to Mr. De La RuIn respect of this mode of representation of the wind records, the Committee are glad to be able to say that it has received the approval of Dr. Romney Robinson, who is admittedly the highest living authority on all aneraometrical questions, and whose instrument has been adopted at the observatorie By his permission, they reproduce the following extract from a letter lately received from hii think the specimen curves which you have sent me are a great improvement on the former one.They are beautifully distinct, and the scale is quite sufficient to convey all needful informatioThe velocity lines in particular are a great improvement.Notwithstanding their want of parallelism, their extremities form a sufficient approximation to the velocity curve, of which I spoke in my last letter to you, to make an exact delineation of that curve unnecessary.In addition, the rainfall has been inserted for all the observatories at which it was measured at that tim The entry is made at 9 a., and refers to the preceding 24 hourThe accompanying diagram shows the exact size of these zinc plates, and contains the record for the observatory at Falmouth, for the storm in questioThe next step is to bring five of these zinc plates into a row with their fiducial lines carefully.