April 7, 1898] 



NATURE 



551 



rooted opinion that prevented Watt and Cavendish from doing 

 full justice to their own theory ; while Lavoisier, who had 

 entirely shaken off these trammels, first presented the new 

 doctrine in its entire perfection and consistency. 



We thus see that each of these eminent men played an inde- 

 pendent and, we may say, an equally important share in the 

 establishment of one of the greatest scientific truths that the 

 eighteenth century brought to light. 



As regards Watt, the history of this incident serves to 

 bring out only more clearly what we know to be the 

 true character of the man. It illustrates the vigour of 

 his intellectual grasp, the keenness of his mental vision. 

 At the same time it exhibits his love of truth for truth's 

 sake ; his unaffected modesty, and the sense of humility that was 

 not the less real because accompanied by a sense of what his 

 inherent love of rectitude taught was due also to himself. The 

 voice of envy and detraction has not been unheard amongst the 

 strife of partisans in the Water Controversy, but throughout it no 

 syllable has been breathed that reflected even remotely upon his 

 honour and integrity. 



SCIENTIFIC SERIALS. 



Several contributions of anthropological interest appear in 

 the January and February issues of Globus. — An old Mexican 

 terra-cotta figure in the American Museum of Natural History is 

 described and figured. It was discovered near Texcoco, and 

 represents a warrior in a padded coat of mail. The figure is of 

 lile-size, and its workmanship is peculiar to Mexican antiquities. 

 — A description of the temple-pyramid of Tepoztlan, by Dr. E. 

 Seler, contains not only interesting details, but several very good 

 illustrations of the plan and construction of the temple. 

 Tepoztlan is the place where the Mexican kings had their famous 

 pleasure gardens, and the inhabitants have preserved their ancient 

 language and many of their old customs in their mountain home. 

 The temple lies 2000 feet above the town on a cliff. The ruins 

 consist of several buildings of all kinds and sizes, which are sug- 

 gested to have been the dwellings of the priests. The temple 

 itself has massive walls built of black and red volcanic stone. 

 The inner space is divided into two rooms by a door let in a 

 thick wall. In the iftner room was found a rectangular cavity 

 containing coal and two pieces of copal, showing probably that 

 here was the place where the holy fire was burnt. The door 

 leading to the inner room is flanked by two pillars, richly carved, 

 but the most interesting feature of the room is its benches of 

 sculptured stone. In this room stands an idol, and there were 

 found two pieces of sculpture : one a bas-relief painted in dark 

 red, the other a relief of a Mexican king's crown. Altogether, 

 this is a notable discovery ; and if it is really the fact that these 

 people have preserved their ancient culture, it is greatly to be 

 hoped that a scientific exploration will be undertaken before it is 

 too late. ^ — Another people of South America is noted in a paper 

 by Dr. Ehrenreich on the Guayaki in Paraguay. Their territory 

 is bounded on the east and south by Parana, on the north by the 

 rivers Acaray and Monday, and on the west by well-wooded 

 hills. Very little is known about them, and only few ethno- 

 graphical specimens have found their way into museums. The 

 personal possessions of the people consist of a conical-shaped 

 cap made out of a jaguar skin, chains made of pierced teeth and 

 bones of animals, stone axes, bows and arrows, lances made out 

 of the bark of the palm, and a sharp instrument made out of 

 animal bones. Their vessels are particularly remarkable. Some 

 are egg-shaped, and obviously intended to fix in the ground, and 

 most of them belong to the so-called basket pottery. Several 

 illustrations accompany the paper, including three photographs 

 of a Guayaki man. He is very short, with strikingly short legs, 

 long arms, broad shoulders, short neck and large head. They 

 live entirely as huntsmen, without any tillage, and the very 

 primitive character of the race suggests that they, and possibly 

 other tribes on the boundary line of Brazil, would reveal much 

 information of value to the anthropologist. — An account of the 

 Moplahs of the coast of Malabar, by Dr. Emil Schmidt, is ex- 

 ceedingly useful. They are partly of Hindoo and partly of 

 Arabian origin, and the mixture is shown in their customs. In 

 the north the young husband settles in his wife's house, and the 

 woman's right of succession is admitted ; in the south, male suc- 

 cession is the rule. A careful study of these mixed peoples is 

 much needed. — Dr.'Nehring gives an account of the worship of 

 the ringed snake among the old Lithuanians, Samoyitians and 



NO. 1484, VOL. 57] 



Prussians.— A paper by Mr. C. G. Hoffman, on the Niggers of 

 Washington, contains some notes on the curious superstitious 

 practices of the Voodoo, said to be a survival of the old religion. 

 — Mr. Christian Jensen's paper on the grave mounds and giants' 

 graves in the islands of North Friesland, contains information of 

 special interest to English folk-lorists who have followed Mr. 

 Mac Ritchie's ingenious explanation of some fairy beliefs. 



SOCIETIES AND ACADEMIES 

 London. 



Royal Society, March 10. — "On the Relative Retardation 

 between the components of a Stream of Light produced by the 

 passage of the Stream through a Crystalline Plate cut in any 

 direction with respect to the Faces of the Crystal." By James 

 Walker. 



If the surface of the plate be the plane oi xy, the positive axis 

 of 3 being directed inwards, the relative retardation is T(«i - Mj), 

 where the velocity of light in air is unity, T is the thickness of 

 the plate, and «i, «^ are the positive roots of a biquadratic in 

 n obtained by expressing that Ix + my -H «3 = i is a tangent 

 plane to the wave-surface. Writing the roots of the biquadratic 

 as series proceeding by powers of sin i, and expressing the 

 coefficients (which are linear functions of sin i) as symmetrical 

 functions of the roots, the terms of the series may in general be 

 determined in succession by means of linear equations, and have 

 the form ± o' -f 7, + a" - 7, where 



a = ttfl -H «! sin i -V Og sin^/ -f a^ sin"*/ + . . . , 

 and 



7 = 73 sin^j + 75 sin^/ -(-..., 

 while the relative retardation is 



T(o' - o' + 27). 

 This method fails when the plate is perpendicular to an optic 

 axis, in which case the biquadratic may be written 

 M* -I- (f„ -f Cj sin^z)«2 + l,^ sin^z n + a,, -f a.^ sin-/ + a^ %va^i — o. 

 Neglecting the coefficient of «, the roots are 



±(ir-fp), ±(ir - p), 

 ■K and p being series proceeding by even and odd powers of sin i 

 respectively. Assuming that the actual roots are 



ir-fp-fa, -ir-p-f/S, . • . 

 the successive terms of the series a, ;3, 7, 5 are determined as in 

 the former method, and, as for terms of the fourth order, have the 

 form 



a = - 7 = «.2 sin-/ + ^3 sin*/' -I- a^ sin^/, 



3 = - 5 = ^2 sin-/ - ^3 %\v?i -t- a^ sin''/, 

 so that 



A =2T(p + a). 



Geological Society, March 23.— W. Whitaker. F.R.S., 

 President, in the chair. — The Eocene deposits of Devon, by 

 Clement Reid. A re-examination of the area around Bovey has 

 led the author to think that Mr. Starkie Gardner is probably 

 right in referring the supposed Miocene strata to the Bagshot 

 period. Lithologically as well as botanically the deposits in 

 Devon and Dorset agree closely. The gravelly deposits beneath 

 the Bovey pipeclays are also shown to belong to the same period, 

 and not to be of Cretaceous date. This correction has already 

 been applied by Mr. H. B. Woodward to a large part of the 

 area. The plateau gravels capping Haldon are also considered 

 to belong to the Bagshot period, for they correspond closely with 

 the Bagshot gravels of Dorset to the east, and of the Bovey 

 Basin to the west, and possess peculiarities which distinguish 

 them from any Pleistocene Drift. Several speakers took part in 

 a discussion upon the paper, some agreeing with the author's 

 views, and some were opposed to them. — On an outlier of 

 Cenomanian and Turonian near Honiton,withanoteon Holaster 

 alius, Ag., by A. J. Jukes-Browne. Although an outlying patch 

 of chalk in the parish of Widworthy was mentioned by Fitton 

 and marked on De La Beche's map, it has not hitherto been 

 described. The tract is about 4^ miles south-west of Membury, 

 3^ miles east of Honiton, and about 7 miles from the coast at 

 Beer Head. — Cone-in-cone : additional facts from various 

 countries, by W. S. Gresley. Examples of flinty stone in the 

 " fire-clay series" of the Ashby coalfield exhibit "areas of conic 

 structure lying unconform.ably. " In the same stratum of shale 

 are large masses of the same flinty rock, more or less coated with 



