December 26, i<^95] 



NATURE 



189 



When the high-pressure area is moving in from the west, clear 

 and colder weather anticipated, with the probability that the 

 early morning temperature will permit the formation of frost— 

 the most important elements to be considered, in determining 

 whether or not frost will occur injurious to growing crops — are 

 as follows : 



(i) Has rain recently fallen, and what is the condition of the 

 soil relative to the amount of moisture contained ? 



(2) What are the natural properties of the soil relative to the 

 slow or rapid loss of heat by radiation ? 



(3) To what degree of heat has vegetation been subjected 

 during the period immediately preceding ? 



The early fall frost injurious to tender crops occurs with the ob- 

 served town or telegraph minimum temperature ranging from 40° 

 to 50°, because, when the early morning temperature in the town 

 falls much lower than 40°, it is usually so late in the season that 

 all crops are gathered, or, if not gathered, they have been de- 

 stroyed ere this condition arrives. At the time, then, that frost- 

 warnings are of the most benefit, we have to deal with the air at 

 temperatures considerably above the freezing-point, and to recall 

 that a deposition of frost requires that the temperature of the top 

 soil, or that of vegetation, be reduced to the freezing point. 

 This, of course, is accomplished by conduction and radiation of 

 heat, which takes place more rapidly from the soil and vegetation 

 than it does from the lower stratum of air to the higher. 



Anything that will seriously interfere with a rapid loss of heat 

 after nightfall will tend to prevent the formation of frost. 

 Moisture does this, and if the soil be well charged it partakes 

 greatly of the stability of water as to temperature, and cools but 

 little, if any, below the temperature' of the superincumbent air, 

 and no frost will occur even though all other favourable con- 

 ditions of clearness, gentle winds, and cool air obtain. Even a 

 small amount of moisture, say one-half inch of rainfall, will 

 give ample protection if well distributed and precipitated within 

 the twenty-four hours previous. But when severe drought 

 conditions are prevalent, injurious frosts may occur when the 

 telegraphic temperatures do not show a reading within ten 

 degrees as low as in the first case. 



I believe that, when estimating the probability or severity of 

 frost, sufficient weight has not been given to the dryness or 

 wetness of the soil, and the resultant dissipation or conservation 

 of heat, and I call special attention to the point as one of the 

 means for improving the forecast. 



I have in mind two typical cases. In the first a high-pressure 

 area attended by clear and cool weather drifted from the west- 

 ward until it covered the State. No rain had fallen with the 

 passage of the low-pressure area immediately preceding it ; 

 hence the ground was in excellent condition for the rapid loss 

 of heat during the night, and a consequent lowering of the 

 temperature of vegetation to the freezing point. Considerable 

 damage was done to cranberries in unflooded marshes. In the 

 second case a high-pressure area of slightly greater weight and 

 slightly lower temperature covered the region about ten days 

 later, but it was preceded within a few hours by a light but well- 

 distributed fall of rain, averaging about one-half an inch, and 

 no frost occurred. In both cases the wind was gentle from the 

 north-west, and the nights were clear. With slightly lower air 

 temperature and higher barometer in the second condition, 

 heavier frost would have occurred than in the preceding case, 

 had it not been for the thinly spread moisture of the timely rain 

 conserving heat at the surface of the earth. 



Might not this principle be carried further in the improvement 

 of the forecast ? Assuming that the caloric energy of the sun is 

 a constant factor, the earth receives each year the same amount 

 or intensity of heat, and as the atmosphere is warmed mainly 

 by contact with or radiation from the earth, seasonal variations 

 of temperature which are marked departures from the normal 

 might result from abnormal terrestrial surface conditions with 

 respect to the conservation of this constant solar energy over 

 large continental areas. Here the excessive or deficient rain- 

 fall during the preceding seasons should receive careful consider- 

 ation. The subject is one that requires deeper and more 

 detailed investigation than the length of this paper will permit. 



I find that the minimum temperatures in cranberry marshes 

 (luring abnormally dry seasons often fall 15° below the tem- 

 peratures telegraphed from the cities and towns within a few 

 miles of the marshes. This is due to the fact that when the 

 loose, spongy peat, of which the marsh is composed to the 

 depth of several feet, has dried out, the radiation of heat 

 during the night is very rapid, and is not counterbalanced by 



NO. 1365, VOL. 53] 



conduction and connection from the marsh. The temperature, 

 therefore, in cranberry marshes is at all times much lower than 

 that which obtains in marshes composed of heavy black muck, 

 where it preserves a more equable condition, such as is common 

 to air resting over a considerable body of water. A dry cran- 

 berry marsh does not, therefore, enjoy that immunity from 

 frost enjoyed by wet marshes and watery lands. But 

 when the ditches are flooded from the reserve water supply 

 on receipt of a frost warning, the water quickly percolates 

 through the peat composing the marsh, and the rapid loss of 

 heat by radiation is checked and the frost averted. 



The amount of heat to which vegetation has been subjected 

 immediately before the frost condition, and the temperature 

 under which it had made its growth, will in a great measure 

 determine the extent of damage to ensue. 



By carefully considering the principles herein enunciated, \ 

 will say that in 1894, twelve out of fourteen official forecasts of 

 frost were fully verified— a much greater percentage of accuracy 

 than has ever been attained by simply considering air conditions 

 alone. 



UNIVERSITY AND EDUCA TIONAL 

 INTELLIGENCE. 



On Friday, the Chancellor of the Exchequer received at the 

 Treasury a large deputation in support of a memorial praying 

 that increased aid may be given to the English University Col- 

 leges, ten in number, and to University College, Dundee, which 

 at present receive among them an annual grant of ;i^i 5,000. 

 Sir M. Hicks Beach, in reply, said there was no question that 

 the existing grant of ;^i 5,000 would be continued ; but he 

 thought that in accordance with the recommendations of two 

 Parliamentary committees a competent inspector should be 

 appointed to visit annually each college receiving a grant, and 

 report on its efficiency, its success, and its financial position. 

 Till such an inspector should have reported, he did not think it 

 possible for him to consider the increase of the grant. 



It is satisfactory to be able to note that the question of the 

 education of mine managers, assayers, and engineers in Australia 

 is actively discussed in the most recent Government reports on 

 mines for several of the Colonies. In Victoria, mining schools 

 have long been established at Ballarat and Bendigo, with branches 

 at the more important mining centres in the Colony. Certificates 

 of competency to act as mine managers are given by these schools, 

 although the holding of such by mining engineers is not compul- 

 sory by law. In like manner in Tasmania, similar certificates 

 are given after a Governmental examination. As the Under- 

 Secretary (or Mil es of Queensland observes in his latest annual 

 report, " the implication is that a certificated mining manager is 

 preferable in the eye of the law to one who has no such creden- 

 tials." In 1893 a school of mines in connection with Sydney 

 University was founded by the New South Wales Government, 

 and ;^io,ooo spent in the election of a suitable building, which 

 has just been completed. The teaching staff has been formed 

 at a small cost by utilising the services of the professors paid by 

 the University, and lectu es and practical instruction are now 

 being given in chemistry, metallurgy, assaying, geology, 

 mineralogy, and all branches of mining to an increasing number 

 of students. Up to the present Queensland alone, among the 

 more important Colonies, has established no mining school ; but, 

 State aid having been p omised to well-supported schemes in 

 any mining centre, the reproach will probably soon be removed. 

 Indeed, some progress has already been made towards establish- 

 ing a technical school at Brisbane. With regard to the effect of 

 such schools, the Under-Secretary of Mines for New South 

 Wales remarks, in his Report for 1894 : '* It is hoped that the 

 establishment of the School of Mines will result in the giadual 

 improvement in the methods of mining, as practised in this 

 Colony, by providing a class of managers who will have had the 

 advantage of a thorough scientific training, and who will only 

 need a few years' practical expei ience to qualify them as mining 

 engineers of the highest efficiency. The ultimate result must be 

 an increased development in the mining industries of this 

 country." In view of this feeling on the part of the Govern- 

 ment officials of the various Colonies, it is evident that the 

 compulsory possession of a certificate of competency by 

 Australian mine managers is almost within sight. 



