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61
Result. Deterioration chiefly marked in work omitted.
Test II. over I. Right = -9.62%
Errors = + .20%
Omissions = — 9.82%
— 19.24%
The same tests were at times given to a control class, working under other conditions, in a
separate room, and it was evident that on the same day a class working under normal conditions could
produce a much better second test than the class under conditions which were abnormal and productive
of deterioration in the working capacity.
The satisfactory nature of the results is confirmed by the fact that, in every case where boys were
working under good conditions, the tests shewed a distinct improvement at the end of the session,
whereas, when the conditions were acknowledged to be bad, the results were always inferior (at the end
of the session). This made the comparison of results easy. The converse is true, namely, if the results
of similar mental tests set before and after school session to a class of ordinarily honest and intelligent
children, shew a falling off or even an absence of improvement in the mental alertness and accuracy, it
is just to conclude that some deteriorating influence has been at work. By methods of exclusion this
is shewn in these observations to be various atmospheric conditions.
Actual Observations. During the summer of 1906 about 25 observations were
made in both boys and girls classes, to get experience with the apparatus and general technique of the
methods. The subjective symptoms of the teachers and children, working under various conditions,
were also analysed, but owing to numerous errors and fallacies, none of these observations are included
here. There was practically no disturbance of any of the school arrangements.
Since October, 1906, numerous observations have been made in which the four chief factors of
temperature, humidity, carbonic acid gas, and movement of the air have been associated in every
combination, and their relation to fatigue indicated. The work was done at Cassland-road in a school
ventilated on the plenum system, so that the temperature of the air could be regulated by means of a
damper and the room kept at any temperature between 50 deg. F. to 80 deg. F.
The records of carbon dioxide were made about every quarter hour, and always with Haldane's
apparatus, each observer making estimations with his own apparatus, and thus checking the other.
Samples of air elsewhere in different parts of the building, and outside were also examined. It was for
instance determined that in one classroom, the ventilation was incomplete in the teachers' part of the room.
On an early observation, when it was attempted to increase carbon dioxide by the action of dilute acid
on marble in beakers, the particulate impurity, consisting of invisible droplets of acid fluid set free by
effervescence, produced such coughing without much difference in the carbon dioxide, that this method
had to be discontinued, and henceforth the carbonic acid content was varied by adding the gas from a
cylinder This latter means was used to alter the carbon dioxide without interfering with the ventilation,
but it was difficult to get any considerable concentration without also blocking the air ducts.
The relative humidity was determined about every quarter hour, from the readings of a standardized
wet and dry bulb hygrometer. This was always swung in the air a few seconds before a wet
bulb reading was taken,so that a maximum evaporation would be produced ; this proceeding reduced the
wet bulb readings by about from 1.2 deg. F. to 2 deg. F. . When local movement was produced by a fan*
the hygrometer was always set near the fan. The hygrometric condition outside was also noted. To
increase the humidity, evaporation of water by boiling kettles over spirit lamps was tried, but it was
found impossible to attain any high humidity with temperatures of 70 deg. or over. This must be
attempted again during hot wet summer weather.
Movement of the air took place by the ordinary currents due to the pressure of the ventilation
system, but was also varied when the ventilation currents were insufficient by means of an electric fan in
the classroom. By this means, evaporation could be furthered when the air was hot and moist, and
much improvement Subjectively could always be obtained.
These observations required continual attention during the whole time. As an example of what
was necessary, the record is given of an afternoon's work, No. 21 in the table, under normal school
conditions.
" January 30. A very fine cold crisp day, clear, with wind N.N.E. outside. Dry bulb, 43 deg. F.
Wet bulb, 39 deg. F. Humidity, 71%. Carbon dioxide in outer air, 3.5.
* A special 16 in. oscillating electric fan was kindly lent for these observations by Messrs. Marples, Leach & Co.