September 21, 1888.] 



SCIENCE. 



141 



is needless to point out what an interest it possesses for the student 

 of the Old Testament, or what important bearings it is liUely to 

 have upon the criticism of the Pentateuch. The most unexpected 

 part of the discovery is the fact that the medium of literary corre- 

 spondence was the Babylonian language and script. It is true that 

 here and there we come across evidences that the writers were not 

 of Babylonian origin, as when the king is called a ' sun-god,' in ac- 

 cordance with Egyptian ideas, or when the first personal pronoun 

 is expressed by the Phttnician anuki instead of the Assyro-Baby- 

 lonian aiiaku. But the language of Babylonia is generally correctly 

 written, and the scribes show that they had acquired a very thorough 

 knowledge of the complicated cuneiform syllabary. It is evident 

 not only that good schools existed throughout western Asia, but 

 an acquaintance with Babylonian literature as well. We can now 

 e.xplain the presence of the names of Babylonian deities, like Nebo 

 or Rimmon, in Canaan, as well as the curious resemblances that 

 e.xist between the cosmologies of Phoenicia and Babylonia. Per- 

 haps the most important result of the discovery is the evidence it 

 afifords us that some parts, at any rate, of the books preserved in 

 the libraries of Canaan, were written in cuneiform characters, not 

 upon papyrus, but upon imperishable clay. There is therefore some 

 hope that when the excavator is able to exhume the buried relics of 

 cities like Tyre or Kirjath-Sepher, ' the town of books,' he will find 

 among them libraries similar to those of Assyria or Babylonia. 

 Not only do we now know that the people of Canaan could read 

 and write before the Israelitish conquest, we also know that they 

 wrote upon clay. The ' scribes ' mentioned in the Song of Debo- 

 rah (Judges V. 6) have become to us living realities. The discon- 

 tinuance of the old literary intercourse, and of the international 

 language and script which accompanied it, must have been due to 

 the advance of the Hittites and their long wars with the Egyptians, 

 followed by the Israelitish invasion of Palestine. Western Asia 

 was for a time a scene of bloodshed and disorder ; Egypt had fallen 

 into decay, and the cultured populations of Canaan were struggling 

 for life and home. On the north were the Hittite tribes ; on the 

 south, the children of Israel. When order began to reign again, 

 the influence of Babylonia had passed away, and its cumbrous syl- 

 labary had been superseded by the simple Phoenician alphabet. 

 The date at which this was introduced into Phoenicia has now to 

 be fixed by the progress of archffiological research. 



ELECTRICAL SCIENCE. 

 Disruptive Discharges and their Relation to Underground 



Cables. 

 The paper read by Mr. E. G. Acheson before the National Elec- 

 tric-Light Association, on the above subject, was the most valuable 

 contribution to our knowledge of underground cables that was 

 given at the last meeting of the association. The object of the ex- 

 periments described by Mr. Acheson was to find out under what 

 circumstances the insulation of a wire carrying a high-tension cur- 

 rent would be pierced by a spark. Some previous experiments on 

 the discharge between points in air led to the equation 

 (E.M.F.)' X (Capacity) 



d= , 



a 

 where d is the spark-length, and « is a constant for the dielectric, 

 the capacity being expressed in micro-farads. For air, a was taken 

 as 135, and (/ was expressed in inches. As the conditions which 

 actually occur in practice are not discharges between two points, 

 but between the cylindrical surface of the wire and some point out- 

 side the insulation, experiments were made to determine the value 

 of a with this arrangement and with different dielectrics. The re- 

 sults give, in general, a greater value of a than when the points 

 alone are used. 



To find what effect cracks in the insulation would have, Mr. 

 Acheson took a broken plate of glass, the two parts of which were 

 held firmly together. With a high electro-motive force, there was 

 no discharge between two points on opposite sides of the glass 

 when the solid part of the plate was between ; but, when the points 

 came abreast the crack, there was a spark. Another interesting 

 experiment showed that a disruptive discharge, due to the breaking 

 of a high-tension cable, would rather go through the insulation 

 than through an electric arc. 



To avoid any chance of a disruptive discharge through the in- 

 sulation of the cable, especially if the latter be lead-covered, Mr. 

 Acheson suggests that a wire be twisted around the outer lead 

 covering, and the point be brought near to the bared surface of 

 the conductor, the distance between them being adjusted until the 

 discharge would pass between the conductor and the point rather 

 than through the insulation. 



In concluding his paper, the author says, " It is safe to predict, 

 that, the disruptive discharge being provided for, little or nothing 

 more would be heard of the much-talked-of pin-holes in the lead, 

 and the moisture-absorbing terminals ; the undergrounding of arc- 

 light cables would become a thing of certainty, and our municipal 

 governments relieved of a great bugaboo. 



The Rechniewski Alternate-Current Motor. — The 

 adaptability of alternating currents for distributing light over an 

 extended area has led a number of inventors to attempt to devise 

 an electric motor that can be used on such circuits. The motor of 

 Mr. Tesla, which has been described in this journal, is one of the 

 most ingenious attempts in this direction, although there is yet 

 considerable doubt as to its efficiency and regulating properties and 

 its adoption would necessitate a complete change in the present 

 method of distribution. It has been known ever since any atten- 

 tion was called to the subject, that an ordinary series motor would 

 work on an alternating-current circuit, and Mr. Kapp has pointed 

 out that a condition of maximum output is that the self-induction 

 and counter electro-motive force of the motor should be equal. 

 M. Rechniewski's motor is of the inverted Edison type, the field- 

 magnets and armature-core being both built up with thin iron 

 plates. The armature is of the drum type, and is large compared 

 with the field-magnets. No data as to the performance of the 

 motor are obtainable, but the following figures, taken from the 

 London Electrician, give some idea of its construction ; — 



Volts at terminal 115 



Current in amperes 100 



Revolutions per minute r,40o 



Diameter of armature 8 in. 



Peripheral velocity in feet per minute 2,800 



Weight of iron in field ' ^40 lbs. 



Weight of iron in armature loS lbs. 



Section of iron in field .. 42.5 sq. in. 



Section of iron in armature 33-5 sq in. 



Induction in armature 3.700,000 lines. 



The motor is not self-regulating, but it can be governed in the 

 same way as some of the continuous-current motors. 



Measurement of Illumination. — M. Mascart has invented 

 a photometer that enables him to compare the illumination pro- 

 duced by two sources of light. The standard lamp illuminates a 

 plate of ground glass, an image of which, formed by a lens, is thrown 

 I after two reflections on a second plate of ground glass, called the ' test- 

 glass.' The general diffused light of the room to be tested illumi- 

 nates a translucent screen, the rays emitted from which are reflected 

 at an angle of forty-five degrees, and fall on the other half of the 

 test-glass. The light from either source can be more or less cut 

 off by sectors. In lighting similar rooms of different sizes, it would 

 appear at first that the source of light should vary in intensity with 

 the square of the dimensions. It is found in practice, however, 

 that the quantity of light varies as the cubic contents of the room. 

 We may, from a consideration of the limiting distance at which a 

 source of light ceases to be effective, get an idea of mean illumina- 

 tion. If, for instance, the limiting distance is ten metres, and the 

 mean illumination one carcel at one metre, then the illumination 

 should be .16 of a carcel per cubic metre. Comparing the illumina- 

 tion of public buildings during this century leads to the conclusion 



