88 



NATURE 



[May 23, 1895 



current increases with the rate of change in the strength of the 

 current { - r )■ a"'' 'his difference is more marked with strong cur- 

 rents than w ith weak. Thus M. Sadovsky has discovered the re- 

 markable fact that for variable electric currents the resistance of 



bismuth changes with any change in -' or — where C is the 



C dt 

 current. The author mentions that the effects observed cannot 

 be due to self-induction, or they would occur when the bismuth 

 is not in a magnetic field. In a note on the above jxiper in the 

 fmmalde Physi<fiu\ M. Sagnac considers what would happen 

 if the same series of experiments wore repeated with an iron 

 wire. A straight cylinclrical iron wire becomes, when traversed 

 by a current C, circularly magnetised ; the energy- due to this 

 magnetisation l)eing, according to Kirchhoff, itk/C-, where k is 

 the susceptibility and / the length of the wire. This energ\- may 

 possibly increase the coefficient of self-induclion by iitKl. From 

 Klementic's data the order of the change in the ap|xirent resist- 

 ance can lie calculated. For weak magnetic fields in which k 

 has a large value, the difference between the value of the 

 apparent resistance for steady currents and for increasing cur- 

 rents may amount to several hundredths of the value of the 

 resistance for steady currents. 



I 



TONBRIDGE SCHOOL LABORATORIES. 

 WWY. often been asked to give some account of the labora- 

 tories at Tonbridge School ; and as they represent some ten 

 years of pleasant lalx>ur on my own part, and a considerable 

 expenditure, joined with much sympathy and help from the 

 Governors of the School (the Company of Skinners), I feel it a 

 privilege to do so. 



It is difficult to render the subject interesting to those who are 

 not concerned in teaching, although as an instance of an ancient 

 foundation lending itself to the most modern of claims, it may 

 appeal to a wider circle. I must ask to be excused from enter- 

 ing upon any treatment of the well-worn subject, scientific 

 education. I am not quite sure that it is any business of mine. 

 In course of time, no doubt, a condition of stable balance will 

 lie reached, as regards the relative weight and value of the various 

 school subjects. Those who are in the thick of the fight cannot 

 always tell which side is winning. 



So far we have little at Tonbridge l)cyond the training-ground 

 itself, consisting of lalmratories and workshops, which may be 

 mentioned in sequence as follows: — 



Wood Workshops. 



Metal Workshops. 



Mechanical Laljoratory. 



Physical Laljoratories. 



Chemical I^lxiratories. 



Engine-rooms with electric light plant. 



Biological l,-ilK)rator)' and Museum. 

 A dc-scription of these in detail is given herewith. 

 Wood lVorkshops.—'V\\ii'M shojjs are well lighted and airy, 

 occupying a ground s|nce of 48 feet by 30 feet. Wfirk-licnches 

 to the numl«r of sixteen, with a|)propriate fittings, allow about 

 sixty lx)ys to work at the same time. A .skilled carpenter is 

 always in attendance for teaching his craft, and a course of 

 graduated tasks are exacted twfore a pupil is allowed to con- 

 struct the .shelves, l)oxes, coal-l)oxes, tables, and other articles 

 which form the staple prrKluce of school shops. 



Metal IVoris/io/is. ~ Th>: wood workshops lead on to the metal 

 sho|)s, in use as well as in fact. They arc under the care of a 

 practical instniment-maker, and the physical lalwratory owes much 

 to his skill. It may Ik; mentiimed here that no physical labor.ttory 

 can Ik.- considered complete unless it is in connection with .suit- 

 able wrirk.sho|)s wherem instruments may Ix; ronslnicled and 

 reinired. TTiese shogis aredevised to accoinmiKlateaUiut twenty 

 lx)ys working together. They are filled with all the necessary 

 apoliances, including planing and drilling machines and six 

 lathes (from 4 in. centre up to 7 in.). The ground s|xice devoted 

 to metal work is 40 feet by 20 feet. After a course of wood- 

 work, lifiys are taught to make their own tools, forging and 

 Ic-mpcring them themselves, to use the file properly, to turn, and 

 afterwanls to conslruri such instruments as they may fancy, it 

 U-ing alw.iys rcrjuiri-)! that a working drawing should be made 

 licforchantl. The favourite (KCU|iation is the construction of 

 electric liclls. •.mall dynamos, microsco|x;s, and levels. 



Mrfhaniial I nhoralo>y.~~'\\\\^ rixjm, which mejusures 40 feet 

 by 21 feet, is fitted for thfwe important lessons in accuracy of 

 olTscrvation to which I give the name of Elementary Physical 



NO. 1334, VOL. 52] 



Measurements, i.e. the measurements of length, mass, and time, 

 and for Practical Mechanics, i.e. the sim]iler measurements of 

 forces and the conditions of equilibrium, the measurement ot' 

 gravitation, and observations of the general properties of matter 

 and the behaviour of matter under stress. All the work-tables 

 are movable, and the walls are fitted with brackets and boards 

 for the support of models and apparatus. 



Physieal Laboratory. — This laboratory opens out from the 

 Mechanical Laboratory, and like it is well-lit .ind lofty. It is 

 42 feet long and 30 feet broad. The centre of the room is fitted 

 with five siilid benches attached to the tloor and provided with 

 gas. These benches are arranged to enable elementary classes 

 to work together at the same experiment. With this object, 

 drawers in the benches are stocked with a large cjuantity of ap- 

 ]>aratus which enables a class of twenty-four boys to work 

 together through a long series of exjieriments in practical 

 physics. Each ex]ieriment has to be represented by at le.isl 

 twelve sets of apparatus for this purpose, and some years have 

 been occupied in organising this branch of work. The work- 

 benches along the walls of the room lend themselves to the more 

 advanced work in practical jihysics. It is needless to say that 

 here the apparatus is not twelve-fold. Beyond the jihysical 

 laboratory is the science master's private room, which has a 

 tendency to shape itself as an advanced physical lalioralory. 



Chemical Laboratory. — This is a fine room, with both sky- 

 light and side windows. It is 45 feet long. 30 feet broad, and 

 30 feet high. Eight benches are fixed, two abreast, across the 

 room, all(.)wing the greatest possible freedom of movement. The 

 benches are arranged to admit forty-eight students working to- 

 gether. They are fitted with shelves for reagents, fixed across 

 the iK'nch, and not lengthways, whereby reaching over one's 

 work is avoided, and also a more complete view and ctmtrol of 

 the whole room is jiossible for the master, l-^ach student is iiro- 

 vided with a most efficient draught-box. serving also as a siip|K)rt 

 for the vessels he is using. This arrangement kee])s the labora- 

 tory thoroughly free from fumes, in spite of all well-meant efforts 

 to the contrary on the ]iart of ]Hipils. The shelves and dr.aught- 

 boxes are removable from the iienches, so that a clear space can 

 be obtained when required for setting tip apparatus on an exten- 

 sive scale. The wall space is occupied by shelves for reagents, 

 and by lead troughs for washing-up jnirposes. By tliis arrange- 

 ment of confining the water-sujiply to ihe walls of the room, 

 mo.st of the ordinary spl.rshing and untidiness of laboratories is 

 avoided. The transverse arrangement of the benches reduces to 

 a minimum the walking about occasioried liy this plan. The 

 cu])boards and drawers of these benches recede, so that it is 

 possible to sit close U|> to ones work. .\ balance-room, 30 by 

 15 feet, leads out from the lalioralory, and liej'ond this is a large 

 theatre or lecture-room capable of seating about 150 boys. The 

 balance-room is provided with chemical balances and books of 

 reference. The lecture-room has a suitably fiirnishetl lecture- 

 table, blackboards, screen for lantern, and cases of minerals .and 

 chemical specimens. 



Liixiiie and Elei/n\ Light A'ooiiis. — The electric light, being 

 used for the main portion of the school, puts the .Science Deiiart- 

 ment in |M)ssession of valuable plant. A gas-engine of 12 indi- 

 cated horse-power, and a reserve steam-engine of 6 indicated 

 horse-power, fitted with a Crosby indicator, together with 

 dynamos and accumulators, give plenty of opportunity for gain- 

 ing a practical knowledge of electric engineering. In addition 

 to this, the current obtained is most tiseful in jiroviding means 

 for practical work and testing in the physical laboratory. The 

 electric light is also used with the mirror galvanometer, to the 

 great advantage of cleanliness and convenience. 



Jiiologiial Laboratory and Miiseiiiii. — It is ajipropriate that 

 the description of this laboratory should come la.st. It is one of 

 the most recent additions to the school, and it shoulil un- 

 doubtedly be the last laboratory for the schoolboy to enter. 

 Biology, unless it is approached through a training in physics and 

 chemistry, is not to be considered as a .suitable subject for pre- 



Itaratory education. Th< roots of biological sciences must always 

 le in physical and chemical ground. 



The room devoted to this work is carefully planned to ensure 

 the most perfect light. The work-benches face windows wliicli 

 come down to the level of the benches, and in the roof is fixeil 

 a goiKl skylight. The workbenches are formed of plate gla,ss, 

 gently sloping at the back into a while glazed guller nmiiing inti> 

 large while-ware troughs or sinks. Walersupply is al Ihe hand 

 of each worker, and the benches can be kept continually (lushed 

 and clean. .Standing aw.ay from the workbench is tlie small 

 writing-table and cupboard, &c., of each .student. The arrange- 



