i86 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1905. 



use of rollable films presents an advantag'e that can 

 scarcely be overrated. By means of a "developing: 

 machine " a whole roll of a dozen exposures can be 

 developed at once, without any need for a dark 

 room or its equivalent, and with a ven,- much greater 

 certainty of a jrood proportion of successful neg-atives 

 than can be claimed for any other method. As a recent 

 experience of what may be expected from such a manner 

 of work, it may be mentioned that a friend of the writer, 

 who does not claim to be even an amateur photographer, 

 made a few months ago about three hundred and fifty 

 exposures in and near the Soudan, and of these he has 

 lost only ten or a dozen, which were spoilt by faults 

 in using the camera, such as forgetting to wind up a 

 new film after expo.«:ure. All the rest are useful, and a 

 very large proportion technically perfect, without stains 

 or faults. In using the machine — which is only a tank 

 to hold the developer, and an arrangement for wind- 

 ing the length of film into a convenient roll for treat- 

 ment — the best way is to take the developing powders 

 that the makers provide in suitable small packets, and 

 to follow the instructions as to lime, &c., that are given 

 with the apparatus. 



Packing, <tc. — The packing of the stock of sensitive 

 films may well be left to the makers, for their consider- 

 able experience in sending such material abroad may be 

 relied on; but it should be seen that they clearly under- 

 stand where the material is to be taken to. It is usual 

 to put each spool of film into a tin box, and if the lid 

 is made secure by means of adhesive plaster instead of 

 being soldered down, the tins can be used more than 

 once — or for re-packing. 



Rehearsal and General Procedure. — Before starting, a 

 few exposures should be made and developed by way of 

 rehearsal. A spool of six films, and, if necessary, a 

 second similar one, will serve well for this purpose. 

 With the shutter .set at the twenty-fifth of a second, 

 and the lens diaphragm at f/ii, f/i6, and f/22 respec- 

 tively for each of three exposures on a suitable subject 

 in good light, a sufficient idea will he obtained as to the 

 conditions necessary. The exposure meter should be 

 used at the same time, noting the number of seconds 

 required to produce the standard tint. To adjust a sub- 

 sequent exposure to an alteration in the value of the 

 light, as shown by the different time necessary to pro- 

 duce the standard tint in the exposure meter, it is better 

 to vary the lens aperture, for this change can be relied 

 on, each aperture giving double the exposure of the 

 next smaller. The shutter speeds arc generally not 

 exactly as marked, and it is possible that by pushing 

 the pointer to the figure that indicates half the exposure 

 just given, there may be no alteration in the duration 

 of the exposure. \\'ith constant fine weather, it may not 

 be necessary to test the light perhaps for days together, 

 but if the weather changes, or the subject is unduly 

 shaded, as it may be in towns or under trees, then the 

 exposure meter should be used. If a longer exposure 

 becomes necessary than the one suggested, the camera 

 should be supported on or against some steady object, 

 such as a wall, a gate, or a tree. Then, unless the times 

 of the other settings' of the shutter have been experi- 

 mentally determined, it will be best to set the shutter 

 index to " B" or '' bulb," when the shutter will remain 

 open as long as the bulb is pressed, and will shut as 

 soon as it is released. Exposures of a quarter of a 

 second and upward can be easily given in this way after 

 a little practice. 



The Greact Zimbab^ve, 

 RhodesidL. 



Amo.vg the scientific matters which will be considered 

 by the British Association in the course of its visit to 

 South Africa is the question of the origin of the ancient 

 ruins which are scattered so profusely over the whole 

 of Southern Rhodesia — an area extending some six 

 hundred miles from east to west, and five hundred 

 miles from north to south. 



This territory, situated far inland from the shores of 

 the Indian Ocean, appears to have some connection 

 with the ancient history of the Near East, a 

 conclusion resulting from explorations among these 

 ruins which have been carried on during recent years. 

 It is a conclusion which is intense!)' fascinating, not 

 only to the archa?ologist and antiquarian, but to the 

 Biblical student, for here are to be found the remains 

 of an enormous gold-mining industry and the traces of 

 an ancient civilisation, for which Semitic people, most 

 probably from Southern Arabia, are responsible. 



The age of the oldest type of ruined buildings is now 

 believed to date back contemporaneously with, if not 

 earlier than, the Solomonic gold period of Holy Writ, 

 though much later waves of Semitic colonists have 

 undoubtedly carried on in this territory the enterprise 

 of their ancestors. It also appears that the most 

 ancient type of buildings in Rhodesia yields evidence of 

 Phallic religion, and of the worship of Baal and 

 .•\shtaroth as described in the Old Testament. 



The main objective of these successions of colonists 

 was that of gold-winning, for the remains of thousands 

 of gold workings occupy the area in which the ruins 

 are found. So extensive are these gold mines that 

 experts believe that gold to the modern value of at 

 least seventy-five million pounds sterling has been ex- 

 tracted in ancient times from the reefs of this country. 



From the recently-published work* written by Mr. 

 R. \. Hall, F.R.ri..S., who spent over two years in 

 exploring the central group of ruins, we gather that 

 the structures are of various ages covering periods ex- 

 tending from the most remote antiquity down to 

 media;va! times. 



These buildings, which are admitted to be the 

 greatest archccological wonder of the Southern Hemi- 

 sphere, are in groups, but the groups are connected 

 with each other, and also with the coast at the ancient 

 port of Sofala, by chains of massi\c forts at a distance 

 of a few miles from each other, and these forts occupy 

 strategic points protecting well-defined routes of the 

 ancients throughout the country. Messrs. Hall and 

 Neal statet that there are at least some three or four 

 hundred ruins or sets of ruins throughout the region 

 of Southern Zambesia, and descriptions of many of 

 these buildings and of the associated gold workings, 

 together with information as to the ancient architec- 

 ture, are set forth in detail. 



The most important group of buildings is that of the 

 Great Zimbabwe, i.e., " the great buiklings of stones." 

 This is situated some two hundred miles inland west of 

 the shore of the Indian Ocean at Sofala. Zimbabwe, 

 both by the size of its buildings, the area covcretl (one 

 and a half miles by one and a quarter miles), by its 

 position, appears to have been the chief metropolitan 

 centre of the ancient gold miners, and is undoubtedly 



• " Great Zimhabwe" (Methuen) 

 ' Thi Ancient Ruins 0/ Rhodesia " (Metbuen). 



