328 



NATURE 



\Feb. 22,1872 



sarily that indicated by the number appearing at the same 

 moment uppermost on the corresponding wheels. . 



"The wheels containing the figures are governed by an 

 electro-magnetic motor, which, for 'each observation, sets 

 the three wheel systems successively in motion, until the 

 corresponding wires have reached the mercury in their 

 respective meteorological instruments, when the above- 

 mentioned electrical current instantly arrests the motion, 

 so that accordingly all three steel wires stop with their 

 lower extremities each in contact with the surface of the 

 mercury in its respective instrument. The numbers there- 

 fore that stand uppermost on the numbered wheels are 

 just those which indicate the height of the barometer and 

 of the two thermometers, and now the same electro- 

 magnetic motor operates upon a printing apparatus which, 

 after having deposited colour on the type, presses the 

 slip of paper against them. This being done, the steel 

 wires are drawn up again by the motor, which stops as 

 soon as a certain distance from the mercury is attained, 

 and all is ready for the next observation. 



" The interval between the observations is a quarter of 

 an hour." 



Attention is then directed to the following considera- 

 tions : — 



"The instrument delivers the observations in a form in 

 which they may immediately, and without further modi- 

 fication, be used by the meteorologist in his work. 



"A very large number of very carefully made compa- 

 risons have shown that the observations registered by 

 this method possess an accuracy equal to that which is 

 generally attained by ocular observation. 



" The zinc vessel, in which the upper ends of the ther- 

 mometers are enclosed, is so air-tight that it is found 

 possible, by means of chloride of lime and caustic potash, 

 to keep the enclosed air always free from damp and car- 

 bonic acid, a precaution which it will be easily understood 

 is necessary in every climate where the temperature is 

 liable to sink below the freezing-point, but is still further 

 necessary to protect both the mercury and the steel 

 wires from oxidation, and thus preserve the galvanic 

 contact. 



" A meteorograph of this construction has for two years 

 and three-quarters been in use at the Upsala Observatory, 

 executing six observations every hour, without any per- 

 ceptible alteration of the surface either of the mercury or 

 the steel wires, that could in any way affect either the free 

 efficiency of the instrument or its degree of accuracy, 

 which throughout the whole time has been found to be 

 that above named. 



" As the clock which determines the time of the obser- 

 vations does not require winding up — the instrument itself 

 restoring the tension of the mainspring every quarter of 

 an hour— it continues to go A long as the driving force, 

 i.e., the electrical current, is maintained ; and, as the slip 

 of paper applied lasts fully three months, it is clear that 

 that is the period for which the instrument may be left 

 to itself. The work then requisite is little more than to 

 take out, cut, and sew up in order the paper of observa- 

 tions, and replace it with another slip. We thus see that 

 this instrument requires but very little time and labour of 

 the person who t.ikes charge of it. 



" It is entirely for special reasons that the construction 

 of the instrument has been limited to the registration 

 of thermometrical, psychrometrical (hygrometrical), and 

 barometrical observations, for the method may be applied 

 advantageously to observations of the course of any phe- 

 nomena whatever, provided they can be indicated by an 

 index admitting of galvanic contact. It is, therefore, 

 applicable for all the now usual kinds of meteorological 

 observations, and nothing prevents the same instrument 

 executing and printing them all in one and the same 

 table." 



The following is an extract (giving one hour's instru- 



mental readings) of one of the printed forms referred 

 to in the first paragraph: — 



1 . . 57 . . 130 . . 673 



57 . . 1305 • • 6725 



57 . . 132 . . 672 



57 ■ • 133 ■ . 673 



2 . . 57 . . 1335 . . 672 



The width of the slip of paper used in these obser- 

 vations is 4'25 in. 



In the Exhibition meteorograph, the timekeeper (re- 

 ferred to in the eighth paragraph) is merely a watch-move- 

 ment of moderate size.* In the place of the ordinary 

 minute-hand there are four, fitted on the same centre and 

 projecting from each other at right angles in the form 

 of a cross ; in other words, the points (one of which 

 resembles what is technically termed a spade- hour hand, 

 and indicates the time) are 15 min. apart. Every time 

 one or other of the hands comes opposite the figure III. 

 it depresses a small steel lever which, through suitable 

 mechanism, completes the circuit. 



I am indebted to Dr. Theorell for a very courteous letter, 

 dated from Upsala, respecting the block used in the 

 original description, also to Messrs. Norstedt and Son, 

 printers to the Swedish Government, for supplying tne 

 with an electrotype copy of the same through the Swedish 

 Consulate. John James Hall 



ON SLEEP -\ 



PROFESSOR HUMPHRY commenced his lecture 

 by giving a brief account of some of the changes 

 that take place in the tissues when their function is 

 active, and explained that during this time a slight 

 deterioration of structure takes place, which, affect- 

 ing the voluntary system, the muscles and hemi- 

 spheres of the brain, causes the sense of tiring, and 

 necessitates a period of rest for the restoration of the 

 tissues to their former condition. In the case of the 

 muscles this rest is provided for by periods, quickly alter- 

 nating periods, of action and cessation of action. But in 

 the case of the brain, the actions upon which conscious- 

 ness, volition, &c., depend cannot be thus frequently 

 suspended. Their continuance is needed for the safety of 

 the body during long periods, through the whole day, for 

 instance ; and longer periods are therefore required for 

 repair. These are the periods of sleep. 



He next took a cursory glance at the different parts of 

 the nervous system, explaining that the upper regions of 

 the brain are those which minister to consciousness and 

 volition, the intellectual operations, &c. He shov/ed that 

 the functions of these regions not only can long be sus- 

 pended without interfering with the action of the lower 

 parts of the brain, which are more immediately necessary 

 to life ; but that tlrey are very easily suspended — slight 

 causes, such as a jar, or a shock, or an alteration in the 

 blood current, being sufficient to stop the action of these 

 parts and deprive the person of consciousness. The 

 spontaneous stopping of their action, consequent on the 

 slight deterioration of their structure from the continuance 

 of their functions during the day, is the proximate cause 

 of sleep during the night ; and the periodic recurrence of 

 sleep is in accordance with the periodicity observed in 

 several of the nutritive functions, and, indeed, witnessed 

 in many of the other operations of nature. 



After observations upon the condition of the brain 

 during sleep, the circumstances that conduce to sleep, the 

 time that should be allotted to it, and other points, the 

 Professor entered at some length into the subject of dreams. 

 These he regarded not, as has been supposed by some, to 

 be a necessary attendant on, or feature of, sleep, but rather 

 to be the result of an abnormal condition. In the natural 

 state we should pass from wakefulness to complete uncon- 



* On the other side of the instrument to that seen in the engraving, 

 t Abstract of a Lecture dehvered at the Royal Institution, on Friday, 

 February 9, by Prof. Humphry. 



