November 29, 1889.] 



SCIENCE. 



363 



The treatment which now gives promise of most general appli- 

 cability and efficiency is the spraying of the plants with a solution 

 of sulphate of copper (blue-stone) or with one of the preparations 

 in which it is the important ingredient, known as " eau celeste," 

 " Bordeaux mixture," etc. It seems very possible, too, that plants 

 may be fortified against the attacks of parasitic fungi, or their 

 susceptibility to such attacks be largely diminished, by special 

 fertilization, for the purpose of introducing into the plant substances 

 which, while not interfering with its growth, shall make it a less 

 congenial soil for the growth of fungi. The line of investigation 

 here suggested has not yet been followed out, although it offers 

 an opportunity for chemico-physiological work which may yield 

 important results. It is obvious, also, that a vigorously healthy 

 plant will resist the fatal influence of parasites far better than a 

 poorly nourished one. 



Much may be done, after a plant is too far gone to be saved, to 

 prevent further spread of the disease, by removing and destroying 

 the diseased parts. It is not sufficient, however, to throw the por- 

 tions removed into the rubbish heap : the spores must be actually 



A NEW RECORDING PRESSURE-GAUGE.' 



In designing the recording pressure-gauge herewith illustrated, 

 the object was to produce an instrument which would be funda- 

 mentally simple, and consequently reliable, and which could be 

 placed upon the market at a moderate cost. 



Fig. I represents the instrument complete, and ready for appli- 

 cation. Fig. 2 shows the pressure-tube with the inking-pointer 

 attached ; the front of the case, dial, and cover of clock, being 

 removed. The pressure-tube A is of flattened cross-section, and 

 bent into approximately a sinusoidal form. A flexible strip £, of 

 the same metal as the tube, is secured at the ends and along the 

 bends, as shown in Fig. 2. The bent tube may be considered as a 

 series of Bourdon springs placed end to end. 



Pressure applied to the tube produces a tendency to straighten 

 each bend, or collectively to elongate the whole. This tendency to 

 lengthen the tube is resisted by the flexible strip B, and thereby 

 converted into a multiplied lateral motion. The inking-pointer is 

 attached directly to the end of the pressure-tube, as shown in Fig. 



destroyed, and this can be effectually done only by burning. A 

 considerable number of fungi produce, in the plants on which they 

 live, resting-spores, which ordinarily remain on or near the ground 

 in dead leaves or stubble, survive the winter, and, germinating in 

 the spring, infect the new growth. In these cases the danger of a 

 severe attack in the following year can be greatly lessened by 

 clearing up and burning all such sources of infection. 



Numerous instances can be cited of more or less common weeds 

 or wild plants so closely related to certain cultivated plants that 

 they are liable to the attacks of the same fungi, and so serve to 

 perpetuate thosfe fungi, and to infect the related cultivated plants 

 when growing near. Evidently, then, such plants should be care- 

 fully and thoroughly exterminated wherever they may prove a 

 soOrce of danger. 



Professor Humphrey then went on to speak of the application of 

 the foregoing facts and principles in the consideration of a few 

 particular fungous diseases. 



W. T. Dennis, commissioner of fisheries for Indiana, has is- 

 sued a call for a State convention of the disciples of the rod and 

 reel, and dog and gun, to meet at Indianapolis, Ind., on Thursday, 

 Dec. 19, at noon. 



2, from which it will be seen that the usual mechanism and multi- 

 plying-devices are dispensed with, since the motion of the tube 

 itself is positive and of sufficient range. The special advantage of 

 this is evident, considering that in all other pressure-gauges the 

 movement of the tube or diaphragm is small, and requires a sys- 

 tem of mechanism to multiply the motion many times before it is 

 available for indicating purposes. These multiplying-devices must 

 be delicately constructed and properly cared for, and even under 

 the most favorable conditions they are liable at any moment to be 

 a source of error. 



In the instrument illustrated the tube is designed for a range of 

 one hundred and eighty pounds per square inch ; for other ranges 

 its sensitiveness may be varied at will by changing its proportions, 

 as length, shape of cross-section, or thickness. The printed charts 

 for receiving the record make one revolution in twenty-four hours, 

 and are provided with radial arcs and concentric circles, the divis- 

 ions on the radial arcs corresponding to differences in pressure ; 

 while those on the concentric circles correspond to the hours of 

 the day and night. 



During the past year and a half, several of the instruments have 



1 Paper read by W. H. Bristol of Hoboken. N.J., before the American Society of 

 Mechanical Engineers, at its meeting, Nov. 21, 1889. 



