556 



NATURE 



[December 4, 1919 



But, still, gravitation had to be left out; and 

 the question from which Einstein began the great 

 advance now consummated in success was this. 

 If energy and inertia are inseparable, may not 

 gravitation, too, be rooted in energy? If the 

 energy in a beam of light has momentum, may 

 it not also have weight? 



The mere thought was revolutionary, crude 

 though it be. For if at all possible it means re- 

 considering the hypothesis of the constancy and 

 universality of the velocity of light. This hypo- 

 thesis was essential to the yet infant principle of 

 relativity. But if called in question, if the velocity 

 of light is only approximately constant because 

 of our ordinary ways of measuring, the principle 

 of relativity, general as it is, becomes itself an 

 approximation. But to what? It can only be 

 to something more general still. Is it possible 

 to maintain anything at all of the principle with 

 that essential limitation removed? 



Here was exactly the point at which philo- 

 sophers had criticised the original work of Ein- 

 stein. For the physicist it did too much. For 

 the philosopher it was not nearly drastic enough. 

 He asked for an out-and-out relativity of space 

 and time. He would have it that there is no ulti- 

 mate criterion of the equality of space intervals or 

 time intervals, save complete coincidence. All 

 that is asked is that the order in which an ob- 

 server perceives occurrences to happen and objects 

 to be arranged shall not be disturbed. Subject to 

 this, any way of measuring will do. The globe 

 may be mapped on a Mercator projection, a gno- 

 monic, a stereographic, or any other projection ; 

 but no one can say that one is a truer map than 

 another. Each is a safe guide to the mariner or 

 the aviator. So there are many ways of mapping 

 out the sequences of events in space and time, all 

 of which are equally true pictures and equally 

 faithful servants. 



This, then, was the mathematical problem pre- 

 sented to Einstein and solved. The pure mathe- 

 matics required was already in existence. An 

 absolute differential calculus, the theory of differ- 

 ential invariants, was already known. In pages 

 of pure mathematics that the majority must 

 always take as read, Riemann, Christoffel, Ricci, 

 and Levi-Civita supplied him with the necessary 

 machinery. It remained out of their equations and 

 expressions to select some which had the nearest 

 kinship to those of mathematical physics and to see 

 what could be done with them. E. Cunningham. 



DISCOVERY OF A MINOAN PALACE AT 



MA LI A, IN CRETE. 

 r^ISCOVERIES of great importance have been 

 *^ made during the course of excavations 

 carried out this year in Crete by M. Joseph 

 Hatzidakis, at a site one kilometre from the shore, 

 near the village of Malia, about twenty miles east 

 of Candia. 



The site of a palace of the Middle Minoan epoch 



has been uncovered, and numerous objects found. 



The containing walls of the palace, the lower 



courses of which consist of poros stone, can all 



NO. 2614, VOL. 104] 



be traced, the dimensions of the building being 

 110 metres in length and 80 metres in width. The 

 interior w^alls, which are of bricks and rubble, are 

 230 metres in thickness, and the floor of the palace 

 is composed of a layer of white earth upon which 

 is a stratum of chalk and sand with a top surface 

 of red chalk paste. The outside of the containing 

 walls was covered with a white chalk wash. 



The palace was destroyed by fire shortly after 

 the end of the Middle Minoan epoch, and probably 

 suffered from the depredations of looters for a 

 considerable time after its destruction. In conse- 

 quence, few objects of value, and nothing intact, 

 have so far been discovered. A very large number 

 of small fragments of gold leaf, however, have 

 been found. For many years past similar frag- 

 ments have been found by the peasants from time 

 to time, and the site became known as "Chryso- 

 lakkos," "The ditch of gold." Capt. Spratt early 

 last century noted the prevalence of such gold 

 fragments on this site. The fragments are derived 

 in all probability from some large bone or wooden 

 objects which were decorated with gold leaf. 

 Bronze was rare, only a dagger blade, a brooch, 

 and a band having been found. 



The fields between the shore and the palace 

 show traces of walls, and in one case a complete 

 house, all of the same date as the palace, and 

 clearly belonging to the town in which the palace 

 was situated. The site of a necropolis was found 

 near the shore, where one grave containing pot- 

 tery of the same date as the palace was opened. 



Minoan pictographic or graphic signs were 

 found cut on various stone blocks in the palace. 

 The double-axe occurred on a large tetragonal 

 pillar, which was of the type found at Knossos, 

 but twice the size. A six-rayed star of a known 

 type also occurred; a similar star with a spray at 

 the end of one of the rays represents a sign not 

 hitherto known. 



The pottery so far discovered is disappointing, 

 no complete or even well-preserved pieces having 

 been found. The best fragments, mostly of cups 

 of the Middle Minoan periods, were found in what 

 appears to have been a shrine. 



Three kilometres to the west of the palace a 

 number of graves of the third Late Minoan or 

 Mycenean period were found. One of these graves 

 was opened, and was found to contain five rect- 

 angular "larnakes," in each of which was a 

 skeleton. 



The importance of the site lies in the fact that 

 this is the only example hitherto found of a palace 

 of the Middle Minoan epoch without an overlying 

 building of later date. The Middle Minoan parts 

 of the palaces of Phtestos and Knossos are over- 

 built with walls of the Late Minoan periods, and the 

 plans and details of the Middle Minoan palaces at 

 these places cannot, in consequence, be definitely 

 ascertained. The existence of a city and necro- 

 polis of the same date as the palace increases the 

 importance of the site. The Late Minoan city is 

 clearly to be found some distance away. The 

 excavations will be continued, and promise im- 

 portant results. 



