The Hurricane Guide | Page 7

which has been well determined, would do well, on touching at any of the ports above named, to take comparative readings with the standards at those ports, and record the differences between the standard, the portable, and the ship barometers. By such means the zero of one standard may be transported over the whole world, and those of others compared with it ascertained. To do so, however, with perfect effect, will require that the utmost care should be taken of the portable barometer; it should be guarded as much as possible from all accident, and should be kept safely in the "portable" state when not immediately used for comparison. To transport a well-authenticated zero from place to place is by no means a point of trifling importance. Neither should it be executed hurriedly nor negligently. Some of the greatest questions in meteorology depend on its due execution, and the objects for which these instructions have been prepared will be greatly advanced by the zero points of all barometers being referred to one common standard. Upon the arrival of the vessel in England, at the termination of the voyage, the ship's barometer should be again compared with the same standard with which it was compared previous to sailing; and should any difference be found, it should be most carefully recorded.
The correction for the height of the cistern above or below the water-line is additive in the former case, subtractive in the latter. Its amount may be taken, nearly enough, by allowing 0��001 in. of the barometer for each foot of difference of level.
An example of the application of these several corrections is subjoined:--
| Attached Therm. 54�㡤3. |Data for the correction of | | | the Instrument. | +---------------------------------------+-------------------------------+ |Barometer reading. 29��409 |Neutral point 30��123 | |Corr. for capacity - ��017 |Capacity 1/42 | | |Capillary action + ��032 | +---------------------------------------| | | 29��392 |Zero to Royal Society + ��036 | |Corr. for capillarity + ��032 |Corr. for altitude above | | | water-line + ��004 | +---------------------------------------| | | 29��424 | | |Corr. for temperature - ��068 | | +---------------------------------------| | | 29��356 | | |Corr. for zero and water-line + ��040 | | +---------------------------------------| | |Aggregate = pressure at | | | sea-level 29��396 | | +---------------------------------------+-------------------------------+
It would greatly facilitate the comparison of the barometric observations by projecting them in curves when all the proper corrections have been applied. This may be accomplished by a much smaller expenditure of time than may at first be supposed. A paper of engraved squares on which the observations of twelve days may be laid down on double the natural scale, would be very suitable for the purpose.[4] The projection of each day's observations would occupy but a short time; and should circumstances on any occasion prevent the execution of it, when the ship was becalmed or leisure otherwise afforded, it would form an interesting and useful occupation, and serve to beguile some of the tedium often experienced at such intervals.
Registers.--For the particular object in view the register need not be very extensive. One kept in the annexed form will be amply sufficient. It should, however, be borne in mind that none but uncorrected observations should find admission; in point of fact it should be strictly a register of ph?nomena as observed, and on no account whatever should any entry be made from recollection, or any attempt made to fill up a blank by the apparent course of the numbers before and after. The headings of the columns will, it is hoped, be sufficiently explicit. It is desirable in practice that the column for remarks should embrace an entire page opposite the other entries, in order that occasional observations, as well as several other circumstances continually coming under review in the course of keeping a journal, may find entry.
METEOROLOGICAL REGISTER kept on board _____ during her voyage from ____ to ____ by ____.
+---------+----+------+-------+------+------------------+--------+----------+ | | | | | | Wind. | | | | | | | | Att. |-----------+------| | | | Date. |Lat.| Long.| Barom.| Ther.| Direction.|Force.| Remarks| Observer.| |---------|----|------|-------|------|-----------|------|--------|----------| | |h. m.| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +---+-----+----+------+-------+------+-----------+------+--------+----------+
The only difference between the above form and one for the reception of corrected readings will be the dispensing with the column for the attached thermometer, and placing under the word Barom. "corrected."
II.--TIMES OF OBSERVATION.
There can be no question that the greatest amount of information, the accuracy of the data supplied, and in fact every meteorological