TRANSACTIONS OF SECTION C. TAL 
Micraster, and the author demonstrated the methods employed to retain the 
accuracy of detail, and yet to convey the impression of the depth of the 
ambulacra. 
Allusion was made to the weariness of eye and brain caused by the fre- 
quent use of a hand-lens, and a contrast noted between this course and the use of 
photo-micrographic prints for obtaining broad and detailed observations of small 
objects. It was pointed out that with the aid of photographic prints the paleon- 
tologist and the artist could meet on level terms, and that the draughtsman would 
by this means be enabled to see the value of minute detail as plainly as the trained 
observer. Further, such was the excellence of the results obtained, that the assist- 
ance of an artist could in most instances be dispensed with altogether, and the 
photographs rendered in collotype and autotype. A proof of the latter assertion 
was afforded by showing numerous silver-prints of Bryozoa and sea-urchins, and by 
the set of collotype plates which illustrated the author’s recent paper on the genus 
Micraster.1 
The question of expense is an important one, for in the paper mentioned six 
hundred negatives were taken to illustrate the details of the test, and it is obvious 
that the cost of employing an artist to make drawings of even a portion of these 
details would be prohibitive. 
The demonstration was illustrated by fifty lantern-slides of sea-urchins, Bryozoa, 
Brachiopoda, and Foraminifera, and care was taken to show examples which would 
bring out the shortcomings as well as the advantages of the process. 
2. Water-zones: Their Influence on the Situation and Growth of Concretions. 
By G. Assott, M.R.CS, 
Many hold the theory that concretions are due to the presence of organic 
remains, and apparently claim that some centre is necessary for their formation. 
The author thinks that many may be otherwise explained, and calls attention to 
the effects produced by the rain-water which passes into and saturates a rock- 
structure. He has noticed on surfaces of sections and of walls of buildings that 
as soon as percolation has come to an end in beds which are horizontal, or nearly 
so, the water breaks up into horizontal lines or water-zones, and subsequently these 
lines are broken up into moist patches of unequal length, extending across a 
section in definite lines, as illustrated by the photographs which he exhibits. 
Hence the soluble substances of the rock, especially lime, iron, and silica, 
will be brought by the saturation water into positions favourable for the growth 
of crystalline and amorphous masses, and these substances as evaporation goes on 
must be redeposited in new situations, which may or may not coincide with the 
position of fossils. The space through which the dissolved substances may travel 
before being deposited has not been determined, but in many cases one or two feet 
seem to be sufficient. 
The author has observed these zones of moisture both on sandstone and lime- 
stone, and thinks it possible that the selective work may go on in the same way 
in clay. Many disconnected facts relating to concretionary growth appear to be 
explicable in this manner, but further inquiry will be necessary to decide what 
are the special influences at work regulating the growth and deciding the form, 
and whether the concretion shall be amorphous or crystailine. 
3. Tubular and Concentric Concretions. By Gruorce Aszort, ILR.C.S. 
After excluding stalactites and pseudomorphs from the list of tubular concre- 
tionary bodies there yet remain a remarkable series of rings and cylinders which 
afford no obyious explanation of their existence. They consist chiefly of lime, 
silica, and iron, and no other substances appear to possess this peculiar property. 
1 OJ.GS. Aug. 1899, vol. ly. 
