March 28, 1878] 



NATURE 



43 



Look in the jar and you will see a slender ribbon of 

 light extending downward through the jar. Elsewhere it 

 is quite dark and black. Here we see the light streaming 

 through the opening in the card, and lighting up the 

 particles of smoke in its path. 



Take off the card, and let the reflected beam fall freely 

 into the jar. The smoke is now wholly illuminated, and 

 the jar appears to be full of light, and every part of the 

 bottle shines with a pale-white glow. 



Put the postal-card on again and let the light fall 

 through the slit. The smoke has nearly all disappeared, 

 and the ribbon of light in the jar is quite dim. Curious 

 streaks and patches of inky blackness run through it. 

 What is this ? Nothing — simply nothing. The smoke is 

 melting away, and the beam of light disappears because 

 there is nothing to reflect it and make it visible. 



This part of the experiment appears quite magical in 

 its effects, and is exceedingly interesting. 



The Milk-and- Water Lamp 



Take away the jar and put a clear glass tumbler in its 

 place. Fill this with water and throw the beam of re- 

 flected light down upon it, and the water will be lighted 

 up so that we can easily see the tumbler in the dark. 

 Now add a teaspoonful of milk to the water and stir them 

 together. Throw the beam of light down once more. 

 This is indeed remarkable. The tumbler of milk-and- 

 water shines like a lamp, and lights up the room so that 

 we can easily see to read by its strange white light. Move 

 the mirror and turn aside the beam of light, and instantly 

 the room becomes dark. Turn the light back again, and 

 once more the glass is full of light. 



Here the minute particles of milk floating in the water 

 catch and reflect the light in every direction, so that the 

 entire goblet seems filled with it, and the room is lighted 

 up by the strange reflections that shine through the 

 glass. 



AMERICAN GEOLOGICAL SURVEYS 

 Missouri 



THE State of Missouri boasts of abundant mineral 

 wealth. Its seams of coal and its stores of iron 

 and lead mark it out as one of the great centres of the 

 future industry of the United States. Such a country 



might have been supposed only too anxious to have its 

 mineral formations accurately mapped, so as to know ex- 

 actly where and how its subterranean resources lie. Yet 

 the history of its official action in this matter is by no 

 means a gratifying one. As far back as the year 1849 a 

 memorial was presented to the General Assembly of the 

 State, praying for the formation of a Geological Survey, 

 with liberal appropriations for constructing maps and 

 publishing reports ; for investigating causes affecting 

 health, the agricultural capacities of different soils, the 

 water system, and the rocks and minerals of the country. 

 It was not until the early summer of 1852 that the State 

 geologist, who, in response to this memorial, was ap- 

 pointed, began operations. Five annual reports, consist- 

 ing for the most part of only a few leaves, appeared up 

 to the year 1861, and, with one exception, contained 

 mere statements of progress. Perhaps the Legislature 

 began to think that the results obtained were not worth 

 the expenditure to secure them. At all events, in 1861 

 the Survey was disbanded. The authorities, however, 

 seem to have been unwilling that the fruits of the long 

 years of work of their geological staff should be lost ; 

 they accordingly arranged to have them published, but 

 finally abandoned this idea on account of the expense. 

 For nine years nothing further appears to have been done 

 in the matter. At last, in 1870, the Legislature once more 

 roused itself to consider the expediency of having the 

 country properly explored and mapped. A " Mining, Me- 

 tallurgical, and Geological Bureau " was now created, and 

 a new State geologist was appointed. This arrangement, 

 however, not proving satisfactory, the act was amended 

 next year, but soon thereafter the State geologist re- 

 signed, and Mr. R. Pumpelly took his place. The body 

 by which the geological work of the State was controlled, 

 now called the " Bureau of Geology and Mines," con- 

 sisted of a board of five managers, with a staff formed 

 of a State geologist, an assistant palaeontologist and geo- 

 logist, an assistant chemist, and such additional assist- 

 ance as might be possible within the limits of an annual 

 appropriation of 10,000 dollars. 



By the spring of 1872 a more liberal spiiithad appeared 

 in the assembly. An additional chemical assistant was 

 allowed, and the annual vote was raised to 20,000 dollars. 

 The Survey now set to work with prodigious vigour. Mr. 

 Pumpelly and his associates undertook an extensive 

 exploration of the iron and coal districts, while the 

 chemists were busy analysing the minerals sent into them 

 from the field. By the end of the year a large mass of 

 information bad been collected, and as the liberality of 

 the Legislature had shown no sign of waning, a large 

 appropriation was asked for the publication of the results 

 obtained in 1872, and another grant for the issue of the still 

 unprinted reports of previous years. Both these appro- 

 priations, amounting to 9,000 dollars in the one case, and 

 3,000 dollars in the second, were voted. Accordingly two 

 volumes duly appeared next year. The Report for 1872 

 was sumptuously printed and illustrated. Moreover, it 

 was accompanied by a monstrous atlas of chromo-litho- 

 graph maps and sections. Some parts of the coal-fields 

 were carefully illustrated by sections to show the structure 

 of the areas and the relative positions of the seams in 

 different districts. Perhaps some of these sections were 

 on a needlessly large scale. Certainly the whole atlas 

 was issued in a style so luxurious as to suggest that the 

 Legislature must not only have become more liberal, but 

 must be anxious to atone for former delinquencies by an 

 almost extravagant expenditure in print and paper. 



But this golden age was not destined to last. Mr. 

 Pumpelly resigned, very shortly after the appearance of 

 his meritorious though costly volumes. His successor, 

 Mr. G. C. Broadhead, who had previously acted as chief 

 assistant-geologist, found the fund at his disposal so 

 depleted by the heavy expenses of the winter and spring of 

 1873, that he had to reduce his field-staff. The Board of 



