Mi 



i:i: KONING AT SEA. 



I:K. ONNOHBAKOB. 



th Mine a* the length on the equator, on account of the paral- 

 leliam of the meridians ; but, in any latitude, the length of a nnall 

 meridional arc (which, without sensible error, may be of one minute) 

 varying with the Meant of the latitude of the arc, the distance, on the 

 map, of an; parallel of latitude from the equator will be equal t<> tin- 

 sum of the secant* of all the minute* in the degree*. Ac., expressing 

 the latitude of the parallel. Now, in the table* of meridional parlt 

 which are given in treatise* on navigation, the number* under the 

 argument* 1 mm., 2 min., 3 rain., *c., express the value* of such minis 

 of Meant*, the length of an equatorial minute (or geographical mil.- 1 

 being unity. Hence the difference between the numbers, in the table, 

 corresponding to the latitude* of two given point*, will express the 

 number of such minute* or mile* on the map between these points. 



By the help of thi* table a triangle may be always constructed with 

 the data of the problem : and the terms required may be obtained by 

 measurement. In the subjoined figure, let A D be the direction of the 



meridian passing through the ship at A, and B A c be her course ; then, 

 if A c be made equal to the distance in mile* by a scale of equal part*, 

 and B c be drawn perpendicular to A D, A B and a c measured mi the 

 same scale will be the difference of latitude and departure as in plane 

 sailing. Now, if A D be made, by the same acale, equal to the difference 

 between the meridional parts which, in the table, correspond to the 

 latitudes of the point A and c, and D E be drawn parallel to B c, D E on 

 the same scale will express, in miles or minutes, the true difference 

 between the longitude* of A and c. 



What has been said may serve as an example of the manner of con- 

 structing the triangle, when the course, the distance, and the latitudes 

 of the two extremities of the distance-line are given, and it is required 

 to find the difference between the longitudes of those extremities. 

 Again, let the ship's course and distance from any point A, and also the 

 latitude of that point, be given, to find the differences both of longitude 

 and latitude. The formation of the triangle A B c is the same as that 

 just mentioned, and A n being measured on the scale of equal parts is 

 the true difference of latitude (in miles or minutes) ; this being added 

 to or subtracted from the latitude of A, gives the latitude of c. Then, 

 with these latitudes, find from the table the difference between the 

 meridional parts, and proceed as before to find the difference of longi- 

 tude. If the latitudes of the ship at two places were given, and also 

 the distance between those places, and it were required to find the 

 course and the difference of longitude : on the meridian line passing 

 through one of the place* A, make A 11 equal to the difference of lati- 

 tude in miles by the scale of equal parts, and make A D by the same 

 Hcale equal to the difference between the meridional parts, in the table, 

 corresponding to the latitudes ; then draw the indefinite perpendiculars 

 B c and D E, and from A as a centre with a radius equal to the given 

 distance describe an arc intersecting B c in c. Join A and c, and pro- 

 duce the line to E ; then L B A c will be the course, and D E, measured 

 as before, the difference of longitude. 



It is easy to perceive that the table of differences of latitude and 

 dejwrtiircs may be used in Mercator's sailing in the same way as it 

 would be employed in plane sailing, if the meridional difference of the 

 latitudes, from the table of meridional parts, be made to hold the place 

 of the simple difference of latitude. Thus, in the second of the above 

 examples, with the given course and distance, find by inspection in the 

 first-mentioned table the difference of latitude; then, having got by 

 addition or subtraction the latitude of the place a,t which the ship is 

 arrived, find in the table of meridional parts the numbers corresponding 

 to those latitudes, and take their difference. Lastly, with this differ- 

 ence, as a simple .,f latitude, and with the course, find the 

 departure by inspection in the first table; this departure is the required 

 difference of longitude. 



Wlirn a ship is in a high latitude, it is necessary to determine the 

 difference of longitude, either by middle latitude or by Mercator's 

 sailing, for every particular course on which the ship may have sailed. 

 The daily differences of latitude and longitude being thus obtained 

 the seaman knows, within the degree of accuracy of which his data 

 admit, the latitude and longitude of the ship on any day ; but it is 

 eaay to perceive that the uncertainties respecting the estimates of the 

 distances run, the variation* of the needle, the effects produced by 

 currents, Ac., must, in time, render the result* of the reckoning ven 

 erroneous ; and therefore it i* of the utmost importance to correc 

 them frequently by celestial observations. The determination of the 

 latitude by meridional or other altitude* i* easy ; and that of the longi 

 tude by lunar distances or by chronometers xnonld be made as often 

 01 possible. Errry geographical position thus determined with pre 

 cision serves, by comjnris'in with the rmmlts of the dead-reckoning, to 

 lead to a knowledge of the causes of the errors which exist in the 

 latter, and become* a point of dejxirture for the next succeeding ]x>rtioi 

 of the voyage. 



RECOGNISANCE i* an obligation of record, entered into ' 

 some court of record, or magistrate duly authorised, by which the 

 vu-ty entering into it (the cognisor), whose signature is not necessary, 

 acknowledge* (recognises) that he owe* a sum of money to the queen, 

 or to some private individual, who is called the cognisee. This sum is 

 named the amount of the recognisance. The acknowledgment is gene- 

 rally followed by an undertaking on the part of the cognisor to do 

 some act, such as to keep the peace, to pay a sum of money, to atu-ml 

 to give evidence, Ac. On the performance of this act, the cognisor is 

 discharged from hi* recognisance. On hi* default, the recognisance is 

 'orfeited, and he becomes indebted absolutely to the amount 

 recognisance. A debt on recognisance takes precedence of other debt*, 

 mil Minis the lands of the cognisor from the time of its enrolment. 

 If the recognisance is made to a private individual in the nature of a 

 statute staple, Ac., he may on its forfeiture, by virtue of process 

 directed to the sheriff, oht-iin delivery of the lands and goods of thu 

 cognisor till the debt is satisfied, or proceed against the cognisor in an 

 action of debt, or by scire facias. If the recognisance is made to the 

 crown, it was formerly, in all cases of forfeiture, estreated into the 

 exchequer, and afterwards recovered by process from that court 

 use of the treasury. But now forfeited recognisances taken before the 

 court of quarter-sessions,- or justices of the peace, are enrolled among 

 the sessions records, and recovered by the sheriff; a list of the 

 amounts being yearly returned by the clerks of the peace and town- 

 clerks for their districts respectively, to the lords of the treasury. 

 Where a recognisance has been estreated into the exchequer, th.it 

 court may discharge or compound it according to the justice of the 



*j . 



RECONNOISSANCK is an examination of a tract of country or of 

 the sea-coast ; the latter previously to a disembarkation of troops, and 

 the former preparatory to the march of an army in order either to 

 meet that of the enemy or to take up quarters for the season. 



The military reconnaissance of a country is a duty appertaining 

 primarily to the officers on the staff of the quartermaster-^' 

 though in many cases, such as sieges, etc., it is necessarily carried out 

 by the engineers ; and if the enemy is in the neighbourhood, it is per- 

 formed under the protection of an armed force. It is considered as 

 one of the most essential operations connected with the tactics of the 

 field, and serves as the basis of every movement or combination which 

 it may be proposed to make. 



A general knowledge of a country which is or may become the seat 

 of war that is to say, a knowledge of the positions of its fortified 

 places, the directions of its mountains, rivers, and great roads may be 

 obtained from maps or from geographical descriptions; but that which 

 is necessary for the immediate purposes of a campaign can only be 

 acquired by an actual survey of the ground in detail, and by inquiries 

 made on the spot respecting the means which the country may afford 

 for supplying the wants of the army. 



The Marechal Puysegur (1690) appears to have been the first in 

 modern warfare who regularly performed this duty by examining 

 personally the tract through which the army was to march, or in which 

 it was to encamp, and of deciding beforehand on the best routes and 

 positions. He observes (' Art de la Guerre ') that before his time it 

 had been customary to trust for a knowledge of these points to the 

 reports of the country-people, or of officers who might accidentally 

 have been on the ground. He adds that disasters frequently occurred 

 by the lines <>l' unroll being improperly chosen, and that som. : 

 after fatiguing marches, and after all the labour of encamping had 

 been undergone, the troops had been compelled to abandon the 

 ]" '.-it ions on account of their unfituess. Since that time, armies being 

 more numerous and more widely disseminated, consequently requiring 

 more vigilance in the communication of one part with another, and a 

 greater extent of country for their support, the reconnuissances have 

 been made on a greater scale, and in the military establishments of 

 every nation officers are now particularly instructed in all the details 

 of that branch of service. 



Those who are charged with this duty should be habitual, -<l 

 performance of topographical surveys : in the first place by the most 

 accurate methods and with the best instruments ; and . , -midly, by 

 Mich methods as admit of being practised rapidly on foot or on horse- 

 back. In these cases, an azimuth compass held in tin- hand i, 

 used for observing the angles, and the distances must be obtained by 

 pacing, or be merely estimated by the eye. A micrometer scale, 

 divided to 200ths of an inch, fixed in the eye-piece of a telescope, will 

 give distances with comparatively great accuracy and great ease, as it 

 is only necessary to see how many divisions an object subtends, and ou 

 arriving at it to measure it, the focal length of telescope having ben 

 previously determined by experiment. A facility in representing on 

 the plan the inequalities of the ground is also highly necessary. 



In making the reconnoissances previously to the march of an army, 

 the whole of the ground between the actual position of the latt< 

 that which is intended to be occupied should be surveyed if the enemy 

 is n'-nr and there is danger of his attacking the columns by surprise ; 

 otherwise- it may be sufficient to survey the j;--miid wi'thin 

 hundred paces on each side of the roada by which the columns 

 march. A complete plan of the tr.-ict of country in which the 

 noiiwanco is made may therefore be required; or it may sin 

 represent on paper the line or lines of march. In cither case the 



