70 



NATURE 



[May 21, 1903 



spring, which bears against the projecting point of the 

 spindle and so controls any lateral movement. 



In addition to the recording cylinder a second clock will 

 be noticed in the illustration. This was introduced because 

 it was found that the pen was inclined to stick to the paper, 

 so that the full range of temperature was not recorded. 

 The clock once in every minute draws the pen away froili 

 the paper, so that it is free to take up its natural position. 

 Hence the trace is made up of a series of dots instead of 

 being a continuous line. The minute hand of the clock is 

 replaced by a wheel in which sixty teeth are cut. Every 

 minute one of the teeth engages with a short pin supported 

 by a flat steel spring. When this pin is pushed aside it 

 draws after it one of the springs referred to above as press- 

 ing against the point of the spindle. The spring at the 

 opposite end of the spindle consequently comes into plav 

 and pushes the spindle in the direction of its length, thus 

 relieving the pen from the paper. 



In this thermometer the motion of the pen for a change 

 in temperature of one degree Fahrenheit is about one inch 

 (4-5 cm. per degree C.) at ordinary temperatures. 



The thermometer selected for description is adapted for 

 securing a continuous record of temperature. When it is 

 desired to use such a thermometer to regulate the tempera- 

 ture, the pen may be replaced by a platinum point which 

 is arranged to complete an electric circuit by contact with 

 a platinum terminal or by dipping into a mercury cup. 

 The current so set up may be used to operate a relay, and 

 so switch on a stronger current, if heating by electricity is 

 employed, or it may actuate some suitable mechanical 

 arrangement for regulating the supply of gas to a stove. 

 When it is necessary to maintain a uniform temperature 

 for days or weeks together, it is most important that the 

 sparking which takes place at the contact should be as far 

 as possible reduced, otherwise the surfaces may become 

 so contaminated that contact is uncertain, or in the case 

 of platinum contacts may fuse together so that the con- 

 tact is never broken. These are difficulties which those who 

 have worked with such arrangements will appreciate. To 

 overcome them it is well to reduce the current through the 

 contact to the smallest possible value, and to place in 

 parallel with the electromagnet which will form part of 

 the circuit a non-inductive resistance. This resistance may 

 be kept comparatively small, even at the expense of a 

 somewhat larger current. A condenser inserted between 

 the points of contact may be of service, but is not so 

 effective as the plan mentioned. 



It may be of interest to give some account of the success 

 which has attended the use of these methods of regulating 

 temperature in connection with the Blythswood dividing 

 engine. The engine is placed in a detached building in 

 a room fifteen feet long, ten feet wide, and ten feet high. 

 Local conditions render it impossible to make use of a 

 cellar. The room has double windows and shutters ; it is 

 warmed by two gas stoves, of which one is controlled by 

 the regulating thermometer. During the greater part of 

 the year this room can be kept at a temperature of 60° F., 

 the variation in temperature being not more than one degree. 



The controlling thermometer in this instance actuates, 

 by an electromagnetic release, clockwork which supplies 

 the necessary power for turning the gas on or off. 



The dividing engine is enclosed in a wooden case inside 

 this room. Originally the interior of the case was heated 

 by electricity under the control of a regulating thermo- 

 meter. The variations in temperature that were introduced 

 by this method were sufficient to produce disastrous results 

 in cutting a diffraction grating. Accordingly the case was 

 surrounded with a lining of six inches of wool, and all the 

 arrangements for securing a uniform temperature were 

 made in the room outside. When this was done it was 

 found that the temperature inside the case fell slowly but 

 continuously. This was shown to be due to leakage of heat 

 through the stand of the machine, which rested on a large 

 stone block. To prevent this a space was cleared round 

 the bottom of the stand, and this space was kept at a 

 uniform temperature by electrical heating. This precau- 

 tion was found to be effective, and the temperature of the 

 case can now be kept constant with very considerable 

 accuracy, the variation in four or five days not amounting 

 to more, than two-tenths of a degree Fahrenheit. 



H. S. Allen. 

 NO. 175 1, VOL. 68] 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — The Public Orator, Dr. Sandys, spoke a» 

 follows on May 14, in presenting .Mr. Robert Bell, LL.D., 

 F.R.S., Director of the Geological Survey in Canada, for 

 the degree of Doctor in .Science honoris causa : 



Magnu n profecto est provinciae maximae penitus explor- 

 andae et scientiarum terminus latius proferendis vitam suam 

 totam dedicasse. Salutamus virum, qui per annos plus 

 quam quadraginta provinciae maximae Canadensis flumina, 

 lacus, montes, campos denique latissime patentes explor- 

 avit ; ibi locis plurimis nomina primus imposuit, et, ipse 

 mortalium modestissimus, flumini a se primum indagato 

 suum nomen ab aliis inditum audivit. Atqui nomen suum 

 non in aqua scriptum, sed provinciae tantae in saxis potius 

 insculptum reliquit ; regionis illius immensae geologiam, 

 geographiam, biologiam, i'rchaeologiam libellorum in serie 

 longa illustravit, et non modo provinciae ipsius terminos 

 ubique definivit, sed etiam scientiarum fines ubique propa- 

 gavit. 



Duco ad vos Reginae Universitatis Canadensis doctorem, 

 Societatis Regiae Londinensis socium, provinciae Cana- 

 densis exploratorem indefessum, Robertum Bell. 



A university lectureship in mathematics, stipend 50/. a 

 year, is vacant by the election of Prof. Larmor to the 

 Lucasian chair. Candidates are to send their names to 

 the Vice-Chancellor by June 3, with statements of the 

 branches of mathematics on which they are prepared to 

 lecture. 



In a report on the administration of the engineering 

 laboratory it is proposed that two readerships, one in 

 mechanical engineering and one in electrical engineering, 

 should be established for Mr. Peace and Mr. Lamb, the 

 present demonstrators ; that two new university demon- 

 strators should also be appointed, and that, in addition to 

 their stipends, each of these should receive certain pay- 

 ments from the fees of students receiving instruction in the 

 department. The growth of the latter under Prof. Ewing's 

 direction may be gathered from the fact that in 1892 the 

 number of students was 39, and the fees 546/., while in 

 1902 there were 211 students, who paid 5005Z. in fees. 

 In the present year there are twelve teachers, in addition 

 to the professor and the two demonstrators, engaged in the 

 work. 



The syndicate report that the new building for the 

 medical school is almost completed, and that the last stone 

 of the Humphry Museum has been laid. A sum of 8062/.. 

 is required for fittings, furniture, electric lighting, and 

 heating appliances. 



The discussion in the Senate on the proposed reestablish- 

 ment of the professorship of surgery turned chiefly on the 

 question whether or not full residence should be required 

 of the professor. If non-residence were permitted, a smaller 

 stipend might suffice, and the field of choice might be 

 widened. Prof. Liveing, Prof. W'oodhead and others urged 

 strongly that the professor's usefulness would depend on 

 his being resident in the University. 



Mr. Edwin Edser has been appointed head of the physical 

 department of the Goldsmiths' Institute, New Cross. 



A CONVERSAZIONE of the Parents' National Educational 

 Union will be held at the Kensington Town Hall on Monday, 

 June 8. The Countess of Aberdeen will preside, and a 

 paper will be contributed by Miss .Mason, founder of the 

 Union. 



The Court of Governors of University College, Sheffield, 

 has adopted resolutions to the effect that in the interests 

 of higher education in the city and district it is essential 

 that Sheffield College shall have the powers and status of 

 a university similar to those granted to Birmingham, Liver- 

 pool, and Manchester, and also that application be made 

 to the Privy Council for a charter. 



The Secretary of State for India has appointed a small 

 committee to inquire and report to him on the question of 

 the expediency of maintaining the Engineering College at 

 Coopers Hill, as a Government institution for the supply 

 of officers to the Public Works Department in India. The 

 committee will be composed as follows : — Sir Charles Cros- 

 thwaite. Sir James Mackay, G.C.M.G., Sir William Arrol, 



