338 



NATURE 



[January 20, 1910 



It does appear plain that the village institutes have a 

 fine opportunity for giving encouragement to continuation 

 rural education ; they not only miss the opportunity, but, 

 at the same time, unwittingly are the cause of there being 

 no demand for an evening school. Opportunities for the 

 village youth to spend aimlessly and uselessly all their 

 spare time are to be deprecated. 



In one West Riding village the infiuence of the opening 

 of a new institute was shown by the total e.Kodus of the 

 members of the existing evening school. Even the moral 

 obligation to complete their attendances, so as to save 

 financial losses upon the school, failed to bring them back 

 again. The billiard-ball was rolling, so opportunities for 

 the making of more fit citizens were sent flying. The 

 result was not a moral triumph for the ex-students. 



May one suggest that in the future some donor of an 

 institute, or someone who by their contribution has made 

 it possible for trustees to lease an institute at a nominal 

 rent to a committee of management, should insert a proviso 

 in their deed of gift that younger members of the institute 

 are to attend continuation educational work at the village 

 school? Such a proviso might be open to elimination if 

 found, after an extended trial, to be prejudicial to the 

 institute's success. 



There should be an educational side to every village 

 institute; it might be an attached rural association or 

 club for the further advance of rural interests. Such an 

 association might hold meetings periodically for discussions 

 upon general agricultural matters. Samples of manures 

 and feeding stuffs, along with a consideration of current 

 values and prevalent adulterants, are important matters, 

 and should be undertaken by the suggested rural club. 

 The leaflets of the Board of Agriculture would be suitable 

 for elucidation and discussion ; their distribution could be 

 carried out by the club. 



Village halls have been in the past the centre of the 

 arts and crafts inovement ; in some parts of the country 

 they are yet. The development of handwork in the 

 elementary schools of the rural districts should again revive 

 the use of the village hall. Such a revival requires funds. 

 The Board of Education and local authorities place at the 

 disposal of committees doing educational work of a 

 manual nature liberal grants. Some of the wealthy trade 

 guilds might be disposed to find funds for a village develop- 

 ment of arts and crafts if the work had an industrial basis. 

 In this way might be developed in the village, as in 

 Germany, a large number of small workshops going hand 

 in hand with agriculture. 



The village institute and evening school would not 

 become competitors by both taking up educational work ; 

 they would become helpers. Admission to the institute's 

 higher work should preferentially be given to those who 

 had thoroughly prepared themselves for it by a satisfactory 

 course of preparatory work at the evening school. In 

 short, the institute would be regarded as the technical 

 school of the village, giving, amongst other work, prac- 

 tical and theoretical instruction on the greatest of all 

 industries — agriculture. 



John B. Coppock. 

 (Organiser for the Rural Districts of 

 the West Riding of Yorkshire.) 



Education Department, County Hall, Wakefield. 

 Avogadro's Hvpothesis (or Law). 



In Prof. Tilden's "Life of MendeWeff " in the current 

 number of the Journal of the Chemical Society, I see that 

 he refers repeatedly to the " law " of Avogadro. Sir 

 William Ramsay, in his " Modern Chemistry," speaks of 

 it as a " hypothesis," and this has surely been, until 

 recently, the practice of chemists. 



I think there is a growing tendency to speak of it as 

 a law. This, doubtless, arises from the strong confirmatory 

 evidence provided by modern physical chemistry. It is 

 desirable, in the interests of students and of exactitude in 

 scientific nomenclature, that some decision should be come 

 to as to which term should be used. This may necessitate 

 very careful definition. 



A discussion of this matter, in which teachers will give 

 reasons for their choice, should prove of value. 



S. H. WOOLHOUSE. 



Parmiter's School. Approach Road, Victoria 

 Park, N.E., January 17. 

 NO. 2099, VOL. 82] 



" A Japanese Priest in Tibet." 



Whatever may be the demerits of Mr. Kawaguchi's 

 "Three Years in Tibet," reviewed in Nature of 

 January 13, the title of the book is, according to the 

 Eastern habit of reckoning, quite accurate. Mr. Kawa- 

 guchi spent part of 1900, all 1901, and part of 1902 in 

 Tibet — three years. A child in Japan, if born on 

 December 31, begins his second year on January i, and 

 on the succeeding New Year's Day may be regarded as 

 having lived for three years, although he may be only 

 367 days old ! C. G. Knott. 



University of Edinburgh, January 17. 



STAm)ARD MEASUREMENT IN WAVE- 

 LENGTHS OF LIGHT. 

 'T^HE employment of the principle of the interference 

 -*■ of two rays of monochromatic light, derived 

 from the same source, one retarded behind the other 

 by having to traverse a longer path, for the produc- 

 tion of rectilinear interference bands constituting a 

 scale of half-wave-lengths, has now been brought to 

 such perfection that this highly refined scale may be 

 used for the measurement of short distances or small 

 movements of any description whatsoever. The ac- 

 curacy is absolute to the tenth part of a scale division, 

 the twentieth part of a wave-length of light, and is 

 actually measurable with the most ordinary micrometer 

 to the one-hundredth of a scale division, corresponding 

 to the two-hundredth part of a wave-length. Now 

 a wave-length of even the grossest radiations em- 

 ployed, those of red light, derived from either cadmium 

 vapour (o'ooo643S mm.) or hydrogen (o'ooo6562 mm.), 

 is a forty-thousandth of an inch, so that the measur- 

 able unit is an eight-milliontli part of an inch. 



The finest trustworthy measurement by mechanical 

 means (such as the Whitworth machine) or micro- 

 metric devices (such as the most refined thickness 

 measurer) is the one-thousandth of a millimetre, or 

 the twenty-five-thousandth of an inch. Moreover, the 

 amount of possible error with either of these mechanical 

 methods of measurement or the interference method 

 is from one to two units of the respective scales. 

 Hence the interference method is only subject to a 

 possible error of one three-hundred-and-twentieth the 

 magnitude of that to which the mechanical mode of 

 measurement is liable. 



The interference method was first seriously em- 

 ployed by Fizeau, who utilised it for the determina- 

 tion of the thermal expansion of crystals and other 

 small bodies. It was materially improved by Abbe 

 and Pulfrich, and more recently both for the same 

 crystallographic purpose and for general purposes by 

 the writer, who has also extended its use to the 

 measurement of the modulus of elasticitv of crystals 

 and small bodies or small quantities of substances in 

 general. 



It will be remembered also that Prof. Michelson, of 

 Chicago, has recently adapted his entirely different 

 mode of producing interference fringes, in this case 

 circular, to the determination of the number of wave- 

 lengths of red cadmium light, which he has proved 

 to be the most homogeneous of all radiations yet 

 known to us, in the French metre. By employing a 

 graduated series of glass-plate ^talons or intermediate 

 standards, each double of the preceding one, com- 

 mencing with a basal one of half a millimetre in 

 which the actual number (1212) of half-wave-lengths 

 was counted, the number of wave-lengths of red 

 cadmium light in the metre was eventually found 

 to be 1,553,163. This number has since been con- 

 firmed by the independent method of Fabry and Perot, 

 in which circular fringes are also produced. 



Three years ago the writer was invited by the 

 Standards Department of tlie Board of Trade to adapt 



