424 TRANSACTIONS OF SECTION E. 



As regards the maps of very early date, it has always been a question ae to 

 how far they were the outcome of mere information collected by travellers with- 

 out any attempt at instrumental measurement, and how far they were based upon 

 some kind of route-surveying and astronomical determinations. At sea, as has 

 been shown, occasional observations were made to determine latitude, but the 

 actual charting of the coast-line, it is more than probable, was sketched in in 

 the roughest possible manner; with little assistance from any kind of instruments. 

 After repeated voyages the navigators would naturally obtain some acquaint- 

 ance with the general configuration of the coast-lines and be able to draw a 

 fairly accurate chart. These rough sketches were sent from one to another and 

 copied by hand by cartographers ; so in course of time quite a good representation 

 was produced. It is indeed remarkable how accurate some of these old charts 

 were, A rough latitude could always be obtained from observation, but it was 

 quite another thing with longitude. Even at the present day there is far more 

 uncertainty about a longitude observation than a latitude, and in early days, 

 before the construction of accurate chronometere, to obtain the difference of time 

 or longitude between two places was a problem which could not be satisfactorily 

 solved with the rough instruments and tables available. Consequently the 

 longitudes on early maps were, as a rule, very wrong. They were generally 

 much too great, as the tendency was, as it is indeed at the present time, to 

 exaggerate the distance travelled. 



As might be expected, now^ and then serious mistakes seem to have been 

 made in the fitting together of .'sections of charts received from various sources. 

 This was probably due to the fact that in many cases they were rough copies 

 from other copies of the originals, and, with no proper means of settling the 

 orientation, the chart would, as likely as not, be fitted on to another at quite a 

 wrong angle. This is doubtless the explanation of some of the grosser errors 

 on many of the old maps. For instance, in the early editions of Ptolemy's maps. 

 1462(72)-1490, to the north of England there is a remarkable mass of land 

 running something like east and west, and projecting a long way in the former 

 direction. This is, of course, meant for Scotland, but it is diflicult to see how 

 it could have got so wrongly drawn. Yet if you suppose the whole mass turned 

 round at right angles, so that the part that goes to the east is placed to the 

 north, you get a much better representation. There seems little doubt that 

 somehow or other the whole thing has got wrongly joined on to England. In 

 later editions of Ptolemy it was corrected. 



The best-known of all the old instruments is the Astrolabe, which is generally 

 supposed to have been invented by Hipparchus about B.C. 150. Ptolemy, and 

 many others after him, introduced modifications in it, some of which were doubt- 

 less improvements, while others, as is the rase with many so-called improvements 

 in more modern instruments, were of doubtful value or merely unnecessary incum- 

 brances. Divested of all elaborations, the astrolabe consisted of a somewhat 

 heavy metal ring suspended from the thumb, or, in the case of the larger 

 instruments, hung on some form of tripod arrangement. Pivoted at the centre 

 was the movable sighting rule or alidade, and the altitude of the sun or star 

 was read off on the graduated circle round the circumference of the disc. 



During the mediaeval ages things were at a standstill, or rather went back- 

 wards, as regards all scientific pursuits, at any rate in Europe. This in a 

 special manner affected geography and map-making. The advance that had 

 been made by the Greeks was arrested, and the knowledge they had gained was 

 lost sight of ; instead of maps being improved by more accurate surveys of 

 explorers and travellers, they were frequently drawn in monasteries by monks 

 from imagination, more or less distorted by religious bigotry. Cartography 

 fared somewhat better in the hands of the Arabs, but many of the maps seem 

 to have been constructed: under the impression that the outlines of all parts of 

 the world must be formed by straight lines and arcs of circles, drawn with a 

 ruler and compass, so that they are of little real value. There were, however, a 

 few notable exceptions. 



It was not until the latter part of the fifteenth century, the time of the great 

 Portuguese and Spanish discoveries, that any real advance was made, but then 

 Europe seemed to awake from a long sleep, and a grand new start was made. 



One of the first acts of King John II. of Portugal (1481-95), whose memory 



